who is the best and cheapest FTTC provider
As ever, these two criteria don't sit well together. You can have cheapest, and you can have best, and ne're the twain will meet.
BT seem to have done a reasonably good job with Infinity.
I can get 8Mbyte/sec down on uTorrent (seeds permitting, of course) pretty much any time of the day.
What you need to do though is change your settings thus:
Tick "Randomise port each time uTorrent starts"
Untick "Enable UTP Bandwidth control / management" (something like that)
Force outgoing encryption
Disallow incoming legacy connections
Change the maximum concurrent connections to 256 and the max per torrent to 64
Limit upstream bandwidth accordingly
Change the "net max transp disposition" to 255
Change the "Max ports halfopen" to 255
I think that's it... seems to work pretty well with me.
Oh and use Peer Block.
BT Infinity #2 - 8.7MBps via P2P ¦ Full 80/20 Sync ¦
BT / Openreach - You've finally done well. Very well indeed.