Try the UK code allocation plan. This is available on the AIS web site here;
http://www.nats-uk.ead-it.com/public...Itemid=11.html
It seems the previous link I posted does not work, but you need section ENR 1.6, pages ENR 1.6-9. This will let you know which unit has been allocated the squawk, unless it is not unit specific.
As for the frequency, you'll need to lok this up in ENR 2. Sorry but this is a bit laborious.