ASeems like each time I cover a cake with fondant the buttercream seems to seep out from the bottom while I'm applying/smoothing, preventing me to have a nice clean edge. Any tricks? What am I doing wrong?

AChilling the cake for 10 or so minutes in the freezer (slightly longer in fridge) to firm up the buttercream helps.

My question is if you've left the buttercreamed cake in the fridge overnight, hiw long should you let it warm up on the side before attempting putting the sugarpaste on? A couple of hours? I have learnt thru experience if the buttercream is too cold it doesn't go on well at all!!! I am thinking of leaving my cake out all morning so the 'core' of it warms up, then sticking it back in the fridge for 10 mins before decorating. Does that sound reasonable?

I'm in the UK so it's not very humid here.