I've had problems with mice eating my pea seeds this year. It's the first time they've ever gone after my pea seeds, but even after I've covered them with netting and put out traps (caught 4) they're still taking them. But I've found an Allotment Diary video on Youtube about sowing pea seeds, where he shows a really simple but clever wire mesh box he's come up with, made from 10mm wire mesh. I'm really bad at making that kind of thing, but I'm going to have a go at making one because it looks very effective and easy to use.