DLM Reset if I change ISP?

If I change my ISP (BT to PlusNet or Sky), will DLM be reset as part of provisioning?

I'm currently with BT Infinity 2 and have been for about 18 month. My speed has fallen from 62 to 41 Mbps down and from 14 to 9 (up) over that time and has never recovered. The biggest drop of speed when a lightening strike touched down in the next street and DLM immediately kicked in. The speed has never recovered.

depends on the package spec.

e.g. if going from 40/10 to 80/20 yes, if going from 80/20 to 80/20 no.

note plusnet use 80/20 for their 40/20 package.

As Chrysalis says, not going from BT 80/20 to PlusNet 80/20 or PlusNet 40/20.
My modem remained synced through the transfer process, only the router had to be touched.

DLM usually works pretty well (if slowly) and if your line is now good should restore your speed. Even if you do get a DLM reset but the line is still bad, any increase you get from the DLM reset will soon be taken away again.