Its not difficult to DIY install it
If your clever with your purchases, you can do things a lot cheaper than what people think.
It would be more than £3k from Abbey though wouldn't it? Considering the cost of the kit is around £3K, they are hardly going to install FOC for you are they?
To put it into a bit of perspective, My supercharger setup was around £8-9K. This also included Larger radiator, Injectors, RFS, Cosworth Plenum, a HKS SC kit, Walbro fuel Pump, 5 Defi Gauges, A HKS wideband & loads of other bits & pieces. The HKS kit was the biggest part of the cost at near enough 50% of the total.
Like I said above, with £3K you can do a lot more than what people will lead you to believe