Nobody resells BT Retail and it's BT Retail doing the blocking.
BT Wholesale does not do blocking, so you just need to make sure of the policy adopted by the ISPs you are interested in.
FTTC is a BT Openreach product, not even BT Wholesale, and is available from BT Wholesale, (then all the normal ISPs on that), TalkTalk and Sky.
My broadband basic info/help site - www.robertos.me.uk
| Domains,website and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 53.4/16.8Mbps @ 600m. - BQM
"Where talent is a dwarf, self-esteem is a giant."
- Jean-Antoine Petit-Senn.
Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.