Dealing with nuisance phone calls from the UK

For the last few days I have been receiving calls to my German handy number that will ring for maybe 3 times and then stop, or if i answer, nothing but a dead line. When I call the number it is a full mailbox.

I checked the number on the web and found a page complaining of the same thing:
http://whocallsme.com/Phone-Number.aspx/01142015606
Their advertising proclaims them as "Telemarketing that gets results", but does not mention that they get results by pestering people. Their details are:

Ant Marketing
1 Clarke Drive
Sheffield
S10 2NS

I have no idea where they got my number, but I have called their office 2 times and asked to have my number removed fro their call lists where the woman apologises and says that she will. It didn't.

Any tips on how to deal with this if it contiunes? I would report it to BT or Ofcom, but I am in Germany with a german mobile supplier and number.

You can probably still complain to Ofcom, since the marketing company is UK-based and thus comes under their rules. You could also try registering with the Telephone Preference Service, although I'm not so sure that will work with a foreign number. Worth a look though.