First car i ever supercharged was my mini, 1412cc engine, highlift kent cams, webber 45's, straight cut dogbox, it was a true gem to rag around on the track, the difference now is there are too many sensors to play around with and an ECU, the mini didn't which is why it was soo easy to tune!
I wouldn't pay £2k at all for any kind of job like this, i would rather take my time, The whole supercharger part is easy, the hardest bit is where to fit it and power it in that engine bay! Intercoolers aren't necessary but they will aid you - If you have the room, I would however fit a blow off valve as you can't spool down a supercharger!!!
It's one mod i seriously need to get on with, luckily i'm not back at work til the 10th so i may have to get cracking on with the mounting gear!
You've just been done by a Twinny!