TonyS

There is nothing wrong with the design of the 360 clutch, brakes or oil seals. Like any car these will suffer with age and lack of maintenance, and occasionally need replaced. Part of the reason people find these problems on 360s is because they last so long and are quite fault tolerant. Comparing them to a any Vauxhall or Ford (even modern ones) is just a joke, try comparing them when they are the same age. If anything the car is over engineered. Although brakes in any car must in top condition if your are going to thrash the car over hilly countryside (believe me I know).

The car does not need disk brakes at the back, the drum are perfectly adequate. Even modern cars don't need them, I really doubt any of them get anywhere get close to overheating, and are probably more of a sales gimic, although disks are a little more reliable with the lack of adjusting mechanisms. Its the front wheels that do most of the braking, the rears are usually attenuated by a pressure reducing valve.
My 940 is huge and heavy and designed for carrying big loads but has punny rear disks which don't wear much.

Things to check:
New brake fluid? old stuff causes brake fade
Good vacuum hose? Engine end get heat damaged after 10 years or so.
Good flexible hose?
Good disks and pads (use OE pads only)? Worn disks can also accelerate brake fade.
Good rear brakes, adjusters, leaking clinders?
Good servo?
Good master cylinder.
Caliper sticking?
Good pressure reducing valve?

Clutches
Front oil seal leaks are common after 10 years, so I guess rear ones can happen to.
Old clutches will have rusted springs and do seem to get stiff over the years, often its just the clutch cable.
Juddering can be caused by bad alignment, but I think 360s are fairly self centering. Oil contamination or just wear is the most likey.

Anyway don't be afraid to take of the drive shaft its not that difficult, but does take a while.

360 GLTs where great little sports cars from the 80s, and many are still going, unlike the comparable front drive XR3i from the same period. I drove brand new 360s occassionally and they were better than any modern car I have driven, including my partners 97 323i which has bump steer at the back and a number of reliability problems (although the limited slip ABS traction control, and self dimming rear view mirror are pretty cool).

The only major design problems 360s have in fact is the rear axle which gets bent from thrashing. This and the other few minor design problems can be fixed. If you can bring a 360 back to original spec it is still a very good car.