Aye, it's sometimes difficult to distinguish plaice & flounders this time of year but they are about. I've had two from blyth pier but that was early January. They should be out in deeper water spawning now returning late April but I guess the littluns must stay local - who knows with this funny weather!!!!
The best way to identify plaice from flounders I find, is to look at the size of their tail Plaice have a much smaller slim tail than flounders.
Hope this helps
SteveF