I went to WIM in Chesham just this last Saturday.
I fitted new wishbones and droplinks on the friday, tried to do tracking and camber with my friend and his garage/tools. He (the experienced mechanic out of the 2 of us) was daunted by the number of variables on the omega and the fact that he'd never done camber at all before. I called WIM not long before 11am the next morning and they managed to squeeze me in even though Saturdays are the busiest day. I told them I was recommended to them but no by who, and they said there was a special deal on Omegas.
Aside from waiting a bit to be squeezed, I was very pleased (Saturday morning kitchen on big screen kept me occupied! lol).
The normal process is that they get the car on their ramp infront of the Hunter Hawkeye 2000 or whatever it's called, and after asking if anything's wrong with the vehicle, measure everything and chat to you about what they're gonna change. All the variables are measured in real time and displayed on the monitor, and get immediately updated (picked up by IR sensors I think). Their program tells them the idea settings (which the owner has worked out himself and are an improvement over the original Vx settings). It also works things out: eg adjust camber off the ground, but measurements are converted to take into account weight of vehicle.
They then give you a table of results; before and after, and also in pictorial form if you request it, which I did (print off of the monitor).
2 guys worked on the car initially then down to one. Both were very friendly and chatted for a while about stuff, omegas, and forums etc! The owner has been a member of OOF for ages (wheelsinmotion).
Also, they assume you're using the car for road, but will do different set-ups depending what you use it for. I know people come along in race season a lot and ask for different things: road / track / drift / etc
The normal price for an omega is £95 + VAT.
The special price for OOF members is £60 + VAT (£72)
Now all in all, I think it's an amazing deal. There are 5 variables on the omega I think (compare that to £30 at Kwik-fit for front tracking only)
They talk you through everything and give you the settings written down.
What more could you want.
I was definately a believer in their product. Car felt better on way back, consumption improved too I think. Even ride height was even too! awesome. money well spent.
Just do any suspension work needed Before you go!!!

I know that's a long post, but there you go! lol Think it covers everything.
I would like to know about the other WIM "franchises". I was only down south for the weekend, but would be good to know of any more local.