If you had free rein over two giant billboards in central London for just under a week, what would you do with them?

That was the question faced by Rebecca Ross,a lecturer in communication design at the Central Saint Martins art school, when she undertook some consultancy work for billboard firm Outdoor Plus. As part of her remuneration, the firm gave her use of two of its electronic billboards, in Holborn and Aldgate.

So, what do do with them? Most of us, let's face it, would probably fill the space with our Instragram feed, or with pictures of cats, or with our Instagram feed about cats. But, as part of the "London is Changing" project, Ross has been collecting anonymised, individual testimonies of why people are leaving or arriving in London. She's using the billboards to highlight her research into the personal stories behind London's migration patterns.

Part of the appeal lay in the chance to highlight a socially conscious message "in an environment, and on a a scale, usually reserved for a sponsored corporate message," Ross says. The London is Changing board in Holborn is running between a Cadbury advert and an advert for the government's Good for Business campaign.

More importantly, though, Ross believes the complex demographics of London aren't thoroughly understood, and are often oversimplified:

The reason it's called "London is changing" and not "London is getting crap" or "London is selling out" or "London is getting too expensive" or "leaving London" is because the situation is actually much more complicated and nuanced than that.

We know anecdotally that there are loads of people coming to London for work from other European countries, for example, where there aren't many work opportunities. Their situation is different to the middle class situation we so often hear about. There are lots of reasons why people relocate – sometimes they're relocating because there are important opportunities here that there aren't elsewhere.

Of course, many are also forced out of London by rising prices: of the 155 responses the project has attracted so far, "most are from people leaving", Ross says. She hopes that the visibility of the billboards will encourage a more diverse range of testimonies, however – and more of those lesser-heard stories of new arrivals in London, who may have been less likely to hear about the project through social networks and university mailing lists.

Once the project is completed, Ross aims to combine the testimonies with more "statistically rigorous" numerical datasets on demographics in different areas (while the testimonies are anonymous, they do ask for respondents' borough). The responses will also be available to download in full online.

Here are a selection of the testimonies collected so far, taken from those that'll be shown on the billboards until Friday. First, the comments from some of those who are moving to London:

...and why others are leaving:

If you've moved to, from, or within London within the past year, or plan to in the next, you can leave your own testimonial for the project here. Responses will be collected until the end of the year.

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