For FTTC then in general I don't think you will have anything to worry about with BT, Sky or Plusnet of the biggies.
Zen and IDNet have a high reputation. I went from O2 LLU to IDNet when I wanted FTTC, and after a year moved to Plusnet. I have no regrets.
Of the resellers we see here, I suggest (alphabetically) Aquiss; vivaciti and xilo/uno.
I don't recall any ongoing general speed issues on FTTC at any of those. Plusnet had some hiccups in evening latency for a few months after going true unlimited but that appears to be sorted.
My broadband basic info/help site - www.robertos.me.uk
| Domains,website and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 59.2/14.4Mbps @ 600m. - BQM
"Where talent is a dwarf, self-esteem is a giant."
- Jean-Antoine Petit-Senn.
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