I don't know if this is predominantly a Virgin Media issue, but we've been inundated by nuisance calls since they talked us into having a phone line (which we didn't really want in the first place).
Right from day one there's been a variety of nuisance calls, usually from so called 'finance related' companies.
The TPS and complaints to OFFCOM appear to be futile unfortunately, and of course the numbers keep changing and new ones are always cropping up.
Uggghh!!
Anyway.
One of the most useful sites out there, when you can get a number is:
http://whocallsme.com
Generally if you type the full number into Google, you'll at least be able to identify the creeps involved, and see the all other poor blighters in the same boat!
It's almost always UK-based (****) companies employing Indian call centres to carpet bomb us with crooked telesales marketing.
No one seems to care except the poor sods getting the calls.