When to lift different potatoe types.

OK, this is my first year with potatoes so please bear with me!

I have planted Maris peer and so far I have lifted 2 lots of those when in flower, one lot had 27 on it the other had 5 I guess that's the wonders of mother nature.

I also have Desiree which I know I am to leave until the foliage dies!

That's where my knowledge ends (and if any of that is wrong please tell me!)

I also have some Nicola planted at the beginning of May, I believe these are second earlies so do i dig up once in flower or after flowering?

Then recently I obtained some chitted Osprey potatoes from freecycle, I got them straight in hoping to push my crop on a little longer, I think these are also second earlies but anyone got any idea when is best to lift Osprey??

Thanks