Last night just before going to bed my wife was closing the front windows when she her a sniffing grunting noise. The when outside to investigate and we came across a pair of hedgehogs in the front garden. When put some fresh cold water out and picked up some cat food (not fish based) just in case them come back. I read that the noise is more thank likely a male trying to impress the female if they are a dating pair. Lovely to watch. This was around 11:45pm.
I think the grunting and snuffling can also be territory disputes related. Coincidently I too had a pair making a good deal of noise last night and I thought they were trying to establish a pecking order for the food I had put out.