There is an existing thread entitled Setanta on TopUpTv. There might be some useful information on there. A search of the database for setanta brings up a couple of hits.

Subscription for Setanta Sports is on 020 1104 8106, 8107 and 8108.

Also 8111 through to 8113.

Your original post was quite a while ago but I've just joined the site so apologies if its no longer of any use. I was also after a number for Setanta and rang 0191 5013601 which is in mackemland (thats sunderland to you). Local phone call so free from a mobile or landline depending on your tariff.

If you ring to cancel (£12.99/month at the minute) they will offer you it for £7.99 for 6 months on non contract terms. I knocked 'em back...credit crunch and all that!  Only sticking point is that you have to actually put it in writing and its 60 days notice from them receiving your letter so your still gonna pay for 2 months worth anyway. Somethig about it being in their terms and conditions (which I didn't bother reading, my bad.) They told me the money comes out on the 16th of the month so you can/could time it nicely!