In reply to Goofyfoot:
Here is another option - overlayering.
This is the concept promoted by Paramo (though they were probably not the first to think of it).
It works for me, but not everyone likes it.
Basically I'll wear a long sleeved base layer and a Paramo smock. Paramo smocks are waterproof but highly breatheable (provided that you don't wear too much under them).
When you stop 'being active' e.g. going uphill, or when you stop, add another layer over the top of the smock. Paramo sell their Torres garments for this role, but I use a Rab Down jacket.
The Paramo smock is warm and can be likened to wearing a waterproof shell and a 100 weight fleece all in the one garment. You may need to manage temperature using zipped vents etc and adopt the idea that you are effectively wearing your waterproof layer all the time (which means you're not carrying it in your pack).
I know this system, and paramo gear generally is a bit of a 'marmite' issue, but after 40 years on the hills and 4 goretex shell jackets (all became non-waterproof) I'll be sticking with Paramo - expensive, but definitely for me, the best system out there.
BTW I also have a Buffalo special 6 shirt - far too warm for active pursuits, but ideal for sitting in a bird hide for hours
N