Another vote for Zen. The only difference that matters really is customer service and when my fibre went down a couple of weeks ago I went from a couple of common support questions (the usual switch it off and back on again) to an arranged engineers visit in about 25 minutes, engineer turned up next day and replaced the failed fibre coupling at the telegraph pole and restored my gigabit fibre connection within a couple of hours.
I’d say that’s the best endorsement I can give, conversely a neighbor has been fighting with BT for close to 6 weeks now just to get his broadband connected and it’s still not done, he was none too pleased when my engineer turned up and it wasn’t for him!! 😀