if it's any reassurance i planted some kelvedon wonder & sugar snaps at the same time,the KW are a bit puny looking but have the beginnings of peas,on the other hand the SS's are huge/healthy looking plants but have only just come into flower~happened almost overnight,like you i was starting to get concerned as up until a couple of days ago they were nothing but leaves~no expert but i'd say hang in there!I guess they're just a later fruiter?

__________________
the fates lead him who will;him who won't they drag.

Happiness is not having what you want,but wanting what you have.xx