Thanks for your replies, appreciated.
So the moral of the story is, slow down. But it's strange that my upper body was totally dry, which for me is unusual, as that's where I sweat quite easy. There is a bonus arising from this tale. My jacket, again waterproof, was very wet in both side pockets so I decided I'd take it back, only had it 4 weeks. So looking round the store, I spotted the jacket that I'd looked at before, but at £150 I'd gone for the one I'm now taking back. The price tag is now £75, "Black Friday" I'm told. But it's Tuesday, who am I to argue. So a full refund on the one that's going back, plus £15.05 gets me the one I originally wanted. Result.