I set off last week to divine Margaret Thatcher's legacy in such contrasting places as the south Welsh valleys and the borderlands of Greater London and Essex. As I did so, I hurriedly packed a bag with a dozen or so books. Among them was an elegant polemic titled Dancing With Dogma, written by her renowned Tory critic Ian Gilmour just after she had left office. Illustrating what a liability she eventually became, one of its chapters begins with a Thatcher quote from 1990, perhaps pointing to the weekend's news about plans for a memorial library and museum: "Do not say it is time for something else! Thatcherism is not for a decade. It is for centuries!"

Gilmour – a leading "wet", who was dismissed from her cabinet in 1981, tore into her policies from the backbenches, and died in 2007 – believed his party was faced with a choice: either to slough off the Thatcher inheritance or to live in the political wilderness. In 1997, he claimed that her brand of zealous free-marketry was on the way out. "Such attitudes," he wrote, "will probably be even less appropriate in the coming decades, when the worship of the market is likely to be on the wane." Tory neoliberalism, he reckoned, "probably reached its peak in the 1980s and early 90s, when the globalisation of the world economy was used to justify every rightwing excess". By the mid-1990s, he thought the social and economic damage it had caused was self-evident, and advised his party: "The balance will have to be redressed."

But no one much was listening. Indeed, in all the noise that has followed Thatcher's passing, one other death has been rather overlooked: that of the kind of centrist, socially concerned Conservatism that could be traced back through all the pre-Thatcher Tory governments of the 20th century to Disraeli and beyond. Every year, if only for a laugh, I go looking for any signs of its revival at the annual Conservative conference, but it is nowhere to be seen. Whichever combination of the mind-boggling number of modern Tory factions MPs and activists support – the Free Enterprise Group, the Cornerstone Group, Conservative Voice, you name it – they are all Thatcherites of one kind or another – her very own Tea Party, much smaller in number than the old Tory party at large, and ever more shrill and uncompromising.

For all that confected noise about gay marriage, what Tory ministers are doing on social security, the NHS, schools and all the rest is largely in line with what their tribe demands. Their rhetoric, now enlivened by the arrival of the Australian campaign guru Lynton Crosby, certainly is. Moreover, whenever there is Tory dissent about what the coalition is up to, it always comes from the right. No Conservatives seem to worry about what austerity is doing to our social fabric, or offer much to the more blighted parts of the UK than a flimsy belief that "rebalancing" between the state and the market will eventually deliver.

In response to bad news about the economy, much the same chorus always goes up, urging labour-market deregulation, further cuts to social security, and attacks on the minimum wage. Such, it seems, will be their prospectus at the election of 2015, for which the mood music is already in place: witness, for example, George Osborne affecting a glottal stop while he apparently tells the employees of Morrisons that even the Church Of England's views of the modern welfare state are "ill-informed rubbish" – a callow fifth-former in a school play about Thatcherism, barely up to the role.

As the more clued-up "wets" well knew, what Thatcher did to Conservatism exposed tensions that have never gone away. If you profess to believe in both the unrestrained market and such old Tory touchstones as family, nation and community, you will sooner or later discover that the former eats away at the foundations of the latter. Vividly ideological politics, moreover, are good fun to discuss, but always in danger of floating off into their own cold orbit.

For proof of this, read the mind-boggling Tory treatise Britannia Unchained, published towards the end of last year. It's a picture of the UK's future – and Thatcherism's belated apogee – sketched out by five of the 2010 Tory intake of MPs, including Liz Truss, hyped up as the "Iron Lady 2.0" and lately heard paying tribute to the way Thatcher made the Conservative Party "the natural home of radical thought".

Its vision is of 60-hour working weeks, an end to "generous" benefits, and deregulated everything – Thatcherism gone mad, with precious little sense of the empathy with millions of Britons that was her trump card. One of its most remarkable passages runs thus: "Once they enter the workplace, the British are among the worst idlers in the world … Whereas Indian children aspire to be doctors or businessmen, the British are more interested in football or pop music." This is what too much ideology can do to you, fostering a cold impatience with fellow citizens, a belief that the only thing standing in the way of utopia is human weakness (communists are often like this too). It would probably also amount to electoral poison.

Every now and again, a twitch within the Conservative soul suggests that at least a few people know this cannot go on. David Cameron's early claims to a gentler, more enlightened kind of Conservatism now look hopelessly cynical but, early on, his old mentor Norman Lamont told Cameron's biographers that he was "more like a Macmillan Conservative" than a Thatcherite. There was also the "red Toryism" advocated by Phillip Blond, a temporary friend of the Cameroons who pointed out that Thatcher had bequeathed to the UK a grim kind of "monopoly capitalism", and that there was a case for "a restored and yet-to-be radicalised One Nation Toryism". Note also the concerns about inequality and irresponsible capitalism among such members of the wider Tory family as Thatcher's former policy chief Ferdinand Mount, and her biographer, Charles Moore, whose authorised account of Thatcher's life is to be published this week.

While writing this, I began to wonder what would happen if the grandees of pre-Thatcher Conservatism were raised from the grave, and confronted with Britain's current problems. They would agree with the basic goal of deficit reduction, but emphasise the protection of society, a key role for the state in sparking economic growth, and a need for fiscal balance to be achieved on a much more measured timetable. They would probably like large swaths of what Michael Gove is doing to our schools, but be much more uneasy about the ideological stupidities being visited on the health service. They would balk at the dichotomy between "strivers" and "skivers", and worry about Scotland, south Wales, and the north of England. Thinking back to Macmillan's admirable record of housebuilding, they might urge a modern equivalent; Disraeli's empowering of councils would inspire them to question whether all that modern Tory talk about localism means anything at all.

They would also behold Ed Miliband, tentatively exploring some of the same themes, and claiming to be in charge of something called "one-nation Labour". Most modern Tories view what he is doing with contempt; Gilmour and his like would wonder how on earth their party had let him get away with it.