Their fax number according to their web site is 0127 360 7361, so you could try dialling around that number to see it one comes up.
Also perhaps you could unsubscribe by emailing them at info@eurochance100.co.uk
Or even faxing them to unsubscribe
I have just looked at their terms and conditions
http://www.eurochance100.co.uk/cgi-bin/lp.pl?SESID=5976280sfjdfhk764700921&file=... and I quote from them here
If you wish to cancel your membership after the initial cancellation period then you must notify us of this in writing (email, fax or letter). The cancellation will take effect at the end of the next playing period (or at the end of the minimum membership period, if later).I guess there lies your answer.