I grow peas in the vegetable garden in the soil and they are watered when the top of the soil starts to look dry. With flowers and peppers in containers I tend to do the same. I am not an expert but I have heard that over-watering is not good. I think I have killed my lettuce in pots due to that.
Last year, my mangetout grew to about two inches and then something came along and scalloped the edge of every leaf. I planted another row and the same thing happened. The only grew to about six inches after that, so, no peas.
I bought a Wildlife Cam which I will set up near the peas to find who the culprit is this year. Someone said there is a wild turkey around. Methinks, he would take bigger bites.
I planted two rows of Chinese cabbage and they totally disappeared, not a sign of them. This was at about one inch high. I have been gardening for forty years and never had this happen.
Good luck with your peas. I expect someone in the UK will have a better answer for you.
Clementine