To me, this sort of troubleshooting is fun. I enjoy it. I have no idea who Virgin Media have working for them, but performance issues are things that most geeks could fix in a day or two if they thought about it. There'll be one or two bottlenecks that performance tools could identify and I'd not expect it to take more than a couple of days, even if it meant some database alterations.
The fault would have to be particularly deep and entrenched to take this long under normal circumstances, so my next guess is that they've currently got a staffing issue when it comes to what they might consider peripheral IT services. I've worked for various places over time and in one of them, you'd see weeks - sometimes months - of engineers being fully booked up, with difficulties in bridging that gap.
This is one reason I'm serious with my offer to help. If the situation is currently so bad that they can't fix a 1-2 day issue over a very long time, then helping them get out of that mess is in the interests of everyone, so as you say, somebody should. The worst that can happen is that someone looks a little embarrassed at the idea of a customer (even one with a lot of experience in IT) helping out and finds ways to get things done.
