There is an FTTC comparison table at https://spreadsheets0.google.com/pub?hl=en&hl=en&key...
I don't know how much it is being kept up to date but gives a good idea of FTTC providers.
Whatever FTTC provider you are using, it will be using the underlying Openreach infrastructure, but the backhaul from the exchange will differ.
The main 'consumer' level providers when I looked about 2-3 months ago were BT Retail (Infinity), Sky, PlusNet (BT owned company but run pretty independently), and John Lewis (who are really PlusNet resellers). I think the others are all quite a bit more expensive, especially if you use a significant amount of data. Here are a few points to watch.
- PlusNet and John Lewis have the best reputation for customer service. (but still rely on BT Openreach to get most things done)
- PlusNet and John Lewis have 100 or 120 Gb download limits (I think), but maybe the PlusNet Plus option gets rid of that?
- PlusNet (and I expect John Lewis) has quite a lot of throttling (well explained on their site); again there is much less if you take the Plus option.
- BT Infinity 2 is genuinely unlimited, but with potentially fierce throttling on p2p.
- Sky is genuinely unlimited, with no p2p throttling. It can be difficult to persuade them to give you an 80/20 service, and it is unclear what the upload speed is on their standard service (it still claims just 2, but many say it is really 10).
Moved (with trepidation) to BT Infinity 2 for upload speed. Happy BE user for several years.