Can I plug a fridge freezer into a short extension lead?
Get an extension lead rated for 13 A. You can get rubberised ones which are a bit tougher - you don't want to skimp on the price.

Make sure it has some provision for mounting it on the wall and do so (use screws that won't rust, like brass or zinc-galvanised). That way, if water gets into the garage (like on those days it rains sideways) it won't get to the extension sockets.

It would be best to make sure that there is no way for condensation on the lead to trickle into either end - the plug end will be ok as that hangs down with UK sockets installed the right way up. For the extension outlet end, you just need to leave the cord hanging downwards a bit.

You might want to label the plugs with sticky labels or a marker pen.

Or you might have a electrician mate down the pub who'll install an extra double socket for the price of the parts and a couple of beers :)