I can't remember the details but I think there was a plan in the 1990s to put together a govt register of contaminated land but it effectively got stamped on by the building industry who didn't want to know (or anyone else obviously). TBF this is partly because the UK is basically nearly all contaminated - or at least a hell of a lot is. I did a bit of work on the Olympic site in Stratford in the run up to the 2012 games and one of the selling points for that bid was that there would be massive remediation of contaminated land on old industrial sites but in the event there was basically none because the land was so polluted, they just membraned the whole thing and left the crap underneath. I was told that when they were digging cores for sampling what was there they were finding huge lead concentrations which from the depth and something to do with the decomposition of the lead they could identify as coming from Roman lead smelting, ie it was about 2000 years old, so tbf the idea of just quickly cleaning this up was pretty far-fetched, especially with the pressure of a no-move deadline. So like most of the other social and environmental outputs of the Olympic bid, it was quietly junked.