Both the Geraniums and the Begonias will be fine if they get frosted - it might damage the topgrowth, but shouldn't be enough to kill the Geraniums (they can withstand up to 10 degrees of frost) and it won't damage the corms of the Begonias either. However, if you're going away, it might be sensible to get those primrose plugs planted and settled before you do - unless you have someone who can look after them whilst you're away.
As far as the Geraniums are concerned, you'll need to reduce the topgrowth by half to two thirds anyway to keep them somewhere dry and frost free overwinter...

As always -Bamboo is spot on with the advice. I would just suggest that you pot on the little primrose plugs into a big seed tray or even individual small pots.
They will be even better and bigger by the time you are ready to put them into their final places that way.
I know they say they are ready now...but a few extra weeks growing on is a real bonus and very worth while!

Thanx very much for the advice. If i pot the plug plants up will they be ok outside as i won't have anyone to come and water them if i put them in the greenhouse while i'm away? I don't have room in my house!

Sure thing - just pop them somewhere fairly sheltered - do you have a cold frame which you can leave open for example? Or just near a wall - out of direct sunshine - and sit them on the soil or sand and they will grow down through and help themselves to any moisture they might need before you get home. With luck you will find them having bulked up nicely and ready for potting on in a month or so! I do that regularly up here in the chilly NE and they thrive beautifully. The nurseries always send things far too soon for us up here and invariably we have to wait for the summer stuff to catch the frosts....so hardening them off outside is just the ticket! Enjoy your trip and come home full of energy....LOL