My 2p worth...
BT - Wouldn't touch them with a bargepole. They were my first 'line of attack' when OR woke up to the fact that FTTP infrastructure was already in place (since 3 years - DON'T ask). Placed an order and was given a number to ring to arrange installation which seems the wrong way round to me. Anyway, after the 3rd attempt and getting nowhere I cancelled the order as they were clearly a lost cause.
Cerberus - Absolutely painless! Have now had flawless service (fingers crossed) since June last year; basic 80/20 profile, actually getting around 75/25 which is more than enough for our present needs. A Kelly crew ran the fibre to the property and fitted the CSP at the location requested, and the OR technician subsequently installed the ONT and spliced in the fibre. All happened as originally arranged by Cerberus. £39/ month - well pleased!
Phone - l left the previous TT Business ADSL service in place until I was happy that the fibre service was working satisfactorily, then after reviewing the options went with Vonage for IP (VOIP) phone service. They ported the landline number from TTB (thereby terminating the TTB service) and we are continuing to use the former landline handsets. We've taken the 'Vonage for Home Premium' service with 'Unlimited UK Mobiles' option, £15/ month. Cheaper IP phone options are perfectly possible, but in our case the similarity with landline service is an important consideration as my wife, who is the main user, is somewhat technophobic.
All-in-all, I'm very satisfied with the current setup. Good luck with whchever providers you decide to go with.
Brexit not withstanding, Happy New Year to all!!
Edited by Mygri (Wed 02-Jan-19 21:56:44)