Upgrading to fibre is always a change of product, with every ISP, and normally involves a minimum term of 12 months or 18 months depending on ISP. That's because Openreach impose a 12-month term on them for new fibre connections.
For a very similar product line to UKFSN at similar prices look at vivaciti, aquiss and Freeola. Also similar but less so, look at xilo/uno.
All of those are well-regarded here.
My personal choice is Plusnet. Five years ago I wouldn't have touched them. They have changed.They are a full ISP of course, not a reseller like the above.
My broadband basic info/help site - www.robertos.me.uk
| Domains,site and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 58.7/14.6Mbps @ 600m. - BQM
"Where talent is a dwarf, self-esteem is a giant."
- Jean-Antoine Petit-Senn.
Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.