In reply to a post by serichards:

Been on A & A since Monday morning. Download speed is now nearly 50mbit! It was 36mbit with Zen. Upload is 8mbit and has stuck so far.

Migrating ISP on the openreach FTTC/VDSL system will cause a DLM reset. You can't compare for a month.

Roughly a month has passed since the change to AA ISP.

55 mbit down and 8mbit up is the new speed. This is the faster product which is different to the 40 max one with Zen. Zen had said there wouldn't be much benefit in upgrading to their higher tier.

It's been stable at around 54/55mbit down and nearly 8 mbit up most of the time. Not seen any of the strange speed drop offs as yet.

Still the same speed. 2 months since switch.

55mbit down and 11 mbit up after nearly a year with AAisp. Improvement has stuck and has improved some more on top.