How do I know when potatoes are ready?

[iwouldgoouttonight]

I've planted Maris Piper potatoes and they've got flowers on and some of the leaves are going yellow at the bottom - does this mean they're ready to dig up? I'm new to this so been reading about earlies/main crop/etc - how do I know what mine are? I thought they wouldn't be ready for a couple of months yet.

dig one and see what you get - if they are tiny then leave them for a few weeks - if they are big enough for you then just dig them as you want them.