It's a good point by RATTER15, but be careful, the courts will not take an OS map or deeds as final evidence of what people are entitled to. Of course, from what you say, nobody in the housing area owns the gravelled area and so no, nobody has a claim to any part of it as it is council owned. There is an equitable principle in law that if you have good moral grounds for claiming land, you can be awarded proprietary possession. Howvever, this is VERY unlikely to even be considered. It would more be a case of 'If you think you have a claim, YOU prove it!' They won't be able to, of course...