There is no such thing as a blacklist of addresses, so if you can't get credit and can see no reason for it go through your credit file, available for free from experian and Equifax (cancel after the free trial, and don't pay for a score as they are a waste of time) as there may well be an error, or something that is pushing it down that you've forgotten about. Have a look around for specialist insurers that deal with the type of cover you want, many of the specialist insurers will need ringing and won't exist on comparison sites and the like. A couple of hours research and ringing should save you a good chunk of money.
Some vehicles seem to be regarded as the spawn of satan by insurers, my mum and dads old car, seat Ibiza 1.9 tdi was ridiculous, last time I looked it was stupidly expensive, over double the cost of insuring myself on civic type r's, golf Gti, Mondeo st220 etc.
Don't know what it was but they hated that car for some reason :-/