Hi Rain,
Yes, you must be patient and wait. The pods will get very dry, sometimes they still have a dull green coloration to them as opposed turning brown, but they will be crispy. You shouldn't be harvesting them until then.
Think of the seeds like a baby growing in a mother's abdomen. To have the most potential to be viable, they must stay in the pod until they are completely ready. If you harvest them early, it is like a premature birth. The farther away from the due date, the less chance of survival.
I know cool, moist, cloudy weather isn't idea for seed saving, but I'm going to go out on a limb in my thinking that it will be ok since peas do well in England and are saved all the time, and England is known for summer weather like yours.
In any case, peas in still moist seed pods won't be viable, so you need to wait :)
Remy

Thank you so much for the advice, Remy. I can tell from your posts you are an expert!

Pea pods still bright green and bulgy.

*sigh*, scuffling my toe in the dirt.

You're welcome