£400!!!
Surely not.
Camcovers, £55.
Seat - probably a connection (was working before) - Free
Handbrake fix for MOT - Free (I'll send you some brand new shoes)
Clunk? Sounds like a new problem, but most likely where you hit that nasty bump. Probably droplinks at £20 pair.
Aux tensioner I agree has had it - £26.
Matrix - reverse flush it, get some forte. £5?
Multirams, all you need is a couple of Vacc hoses to make them work.
Max has an arial he can give you?
And the bulbs, rear washer, etc, allow maybe £15. Scrappy?
That puts the price to fix the niggles at a much more realistic £121.
You worry toooo much 
3.0:
MOT £50
Tax £100
Cam covers i though were £75? including sealant.
wipers all around £30
needs some mats, £30
Monthly insurance £80
heated seat is fubar checked connections
Handbrake prob needs new shoes and pads at the back
exhaust within the year looking at the state/noise of it.
ATF will need changing the stuff that escaped looked very brown. another £50.
2.2 needs tax as well, so thats another £100, needs an oil change, fuel filter which all adds up.
I cannot justify that money for it, not when the 2.2 is in far better shape, and its a better drive.