Depends what the plugs are.

Plugs of Begonia- Geranium (which am guessing is the non-hardy Pelagorium and not the hardy Geranium) I would plant out from May. If you are very near the sea and have a south facing garden which is sheltered then Pelagorium can stay out all winter - certainly in pots in verandahs and balconies rather than in the ground.

I will be very brave, and say plant out when all risk of frost has passed, how's that lol, Derek.

many thanks

Edinburgh - late May.

Agree with MG, have learned the lesson the hard way several times....am beginning to get the message now! Always better to err on the side of caution as it takes them so long to recover from a knock-back. I've started putting mine outside the greenhouse during the day today....I'm in Carnoustie.