OK, I'll try to answer your individual complaints properly now I've calmed down a bit
1996 QV for £2500 - That's too much anyway.
Exhuast needs replacing - On an 8 year old car? Not a surprise at all. Especially when it has a CAT, these create a lot of moisture, and rot the mild steel exhaust sections. Can get a stainless job for £300
Front discs and pads all round - Again, 8 year old car, of course it'll need brake parts replacing.
Wipers knackered - All you mention is a ripped wiper blade. Again, a consumable, replace. That could be the cause of the judder, if not, it's just a case of cleaning the grease out of the motor.
Electric window - As I said, I've never had an old car that didn't exhibit signs of the motor being tired. One way to try to combat this is to use silicon spray on the window runners, make it a bit easier on the old dear.
Tailgate struts - Not a common problem with the 145 as far as I;ve heard, but I can't imagine they'd set you back much from a scrappies. I can try to find you the numbe for RJK in Erith if you like, they seem to stock Alfa parts quite well, and deliver nationwide.
Indicators - I think someone else said this is an alarm problem? I've certainly never heard of it before on a 145, know nothing about how to fix it. Incidentally, I did have this problem intermittently on a Mitsubishi I once owned, and they're a reliable Jap car!
Injector - This is a problem that crops up occasionally. If you do a forum search I'm sure you'll find plenty of advice. £400 for the AFM was a bloody rip-off though I think.
Is this typical?
Well, as I:ve said, I think the majority of the things you've rasied were consumables. It's still not typical for them all to come along at once like this. The car you describe sounds to me like one that hasn't been looked after at all, and is a bit tatty, I'd probably let it go, especially at £2500.
For the record, my car is a 98 with 84000 miles on the clock, and has let me down once in nearly 2 years, it was a temperature sensor and cost £100 for the replacement and labour.
You're not jumping in unaware, you've had the sense to get a mechanic to look over potential purchases, what he ahs said should surely warn you off this one. Find a good one, that he says is OK, and you'll be fine.