Broadband Issues - who to call?

About 4 months ago, our plasterer cut our phone wires.  About a week later, BT came out and setup a new master socket.  Ever since, our broadband has been patchy.  It's now quite slow and it drops 2-10 x a day.  I thought it might be the service/router, and so I changed services (due to change anyway as deal was running out).  No fix to the problem.

Who do I need to call to get this sorted?  Are there independent telecommunications engineers?  Would prefer not to have BT out, as its likely to be something with my internal wiring....

Would still think it's BT's problem to sort out.

I think TM is right.  If BT set the new socket up, I'd say it's on them to fix it.

Thanks - do you think I'll have any issue in that I've waiting 4 months to report a problem with the socket?

I just know that BT has a call out fee that's quite high, and if its your internal wiring, they won't do anything to fix it. and you still have to pay the fee.

What I did was to run a long cord straight from the master socket to the computer. Much better speed. Hooked it back to the wall socket and speed was way down. So it is the wiring of the house. I fixed it by just keeping the long cord running through the hall, plugged straight into the master.

It is a good way to isolate the problem.