Was this increase/change to ADSL2+ anything to do with me changind from fast to interleaved?
I think you were still on ADSL2 after interleaving was turned on.
and why did the homehub just restart on its own?
Because that was when the DLM
reset your sync-time margin from 6dB to 3dB. This causes a re-sync.
How will it get back down to ADSL2?
It won't without manual intervention, or loads of errors making the system change its mind. For now, be happy with ADSL2+ and the higher speed. Deliberately causing ADSL2 is geek-stuff and BT first line support wouldn't even know what you were on about.
On BT, with the Home Hub, I expect the idea is a dead duck anyway, without support setting it. Then if it wasn't the best idea in the world, getting it unset may be even harder. The only practicable way is with an alternative router of your own, where you can force it and revert it easily yourself.
Sorry for all the questions
I like trying to help.
My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost
. Internet connection -
Plusnet Value Fibre.
"Where talent is a dwarf, self-esteem is a giant."
- Jean-Antoine Petit-Senn.