Front brakes sticking

[darrsi]

Looked on Wemoto at replacement pistons and seals. They quote a large and small piston and seal kit. Do I need both? Is one for one side of the calipers and one for the other? I assume I'd need a set for each calipers?

You don't need new pistons unless you know they're damaged or totally rusted. (expensive too)
Once they're out you just tidy them up. Don't be overzealous with them though, as you need them to retain their shape, don't start sanding chunks out of them or they'll leak fluid when you put them back on.
The upper pistons are bigger than the lower one's, so you'll have 2 sizes of seals.