I've sued Taylor Wimpey before (as a resident of the Viewpoint development), and they cave rather easily I have to say, although being a lawyer certainly helped.
In terms of FOI requests, TW aren't a public body, but there is a way that this information could be requested and obtained.
Basically, if you are suggesting that an illegal act has been committed (I don't know whether that's correct), there's potential civil action that could be taken. You could argue that there's been some form of nuisance or other tort that has taken place, and you're then considering legal action against that company for civil damages. Perfectly reasonable.
Your course of action then is a pre-action disclosure application to the Court, arguing that you need that information to assess the merits of the claim. Without the information, you don't know whether the claim has merits or not. The further basis of the application is that if the information is provided, and there is no claim, then the Court's time won't be wasted. Judges love that argument.
As a potential Party to a civil action (they're potentially the Defendant if you can find an arguable tort), then you have every right to make the application, and I would strongly suspect that TW would cave and give you the information you require.
Just my thoughts anyway.