Christmas potatoes, again - where to buy

Just got round to trying to source some seed potatoes, and found that everyone seems to be sold out. Seem to remember there's a supplier who's recommended here quite a lot. Can anyone help please? I'd be really grateful.

does anyone know were i can get hold of second cropping potatoes that you can plant in September ? i haven't a clue were to start looking 

many thanks

BB

sorry for confusion Yorkie, they were merged after kevinp's post