Hi Mate,
Like said above, you could fit the brakes easy..........they come out with no problems and the discs should come out east too...........this will save a fair bit of labour costs.
Tyres..........I had the same. I slipped two new GSD's on the back and moved the pirelli's to the front (only took me about 8 months to scrub these out
). Even if you have a mixed set on for a few months at least it will stager your costs...........(still drives ok)
You should then be looking at Service & DBM £260 + Tyres £230 + Brakes £350
Total £840 worst case........
Should
help soften it a little