Re:
I've yet to find any true waterproof that doesn't 'boil me in the bag' from the slightest exertion.
Because of this I've returned to an old Ventile jacket. This is weird stuff, not properly waterproof when used in single layer, its bulky and hot in double layer (+ expensive!). As it's cotton, it also needs to swell-up with water to become 'waterproof' so you'll always feel some damp with a single layer. And then it feels like wet cardboard! :facepalm:
BUT despite all that's crap about it, if you occasionally treat the surface with a hydrophobic spray, it will keep you 'adequately' dry for about 2-4hrs.
Ventile's one big advantage is that it's much more breathable and comfortable than other waterproofs I've tried, even when wet. I keep mine on all the time as a windproof, and have found this to be far better than treated Pertex jackets, which are less breathable and water resistant.
Finally, Ventile is incredibly tough and will last for years (decades!).
As it's not coated or laminated it can be patched easily...but it's pretty thorn/crash proof - you're not gonna tear it. Oh, and being cotton it's quiet, which I really like.
It is expensive, but you can probably find a single-layer jacket under £100..