Yes, Plusnet is 21CN, (technically BT Wholesale WBMC). The fact they are owned by BT doesn't really come into that, as all land-line non-LLU broadband is BT Wholesale based. (WBC/WBMC/IPSC and maybe still a bit of ADSL Max or Datastream).
Once you sort out the cost of the setup, countered by the cashback, you should be fine on Plusnet Unlimited, even with your phone wherever it is now. Mine is still with BT.
Re the contract v non-contract options, be aware that the non-contract continues at the higher rate even after the 12 months is up. So long-term not a good place to be.
As you are close to the exchange I assume you get a very high speed, for ADSL2+, and you may very well be on Fast Path. If you would like to be able to game you might find having interleaving added adds sufficient latency to take you out of the server compensation zone, with an insignificant effect on the download speed. I would expect Plusnet ro be able to organise that on a trial or revert to Fast Path basis if you were with them.
Don't forget that cashback is never guaranteed until it's in your bank!
My broadband basic info/help site - www.robertos.me.uk
| Domains,website and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 54.2/15.2Mbps @ 600m. - BQM
"Where talent is a dwarf, self-esteem is a giant."
- Jean-Antoine Petit-Senn.
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