How to mouse-proof this hole?

[Carstuff]

Fecking bloody mice

What can I do with this hole to make it bomb-proof? Any solution needs to accommodate the pipe's expansion/contraction.

I can't see the picture, if you posted one, but I've heard that packing a hole with steel wool will deter mice.

Oops. Here's the pic. Trouble is, there's a bit of a void underneath, so wire wool etc might just fall through.

I have heard scourers work. Could you fold them up and pack them in really tightly?

you need a radiator pipe collar. they sell collar and sleeve together in diy shops and plumbers.
here is an example

Chicken wire scrunched up will hold without falling through.

The pest controller we had recommended wire wool and expandable foam (is that the right name for it? The stuff you squirt from an aerosol can)

other holes its caulk and scrubbing metal scourers or steel wool. you bread or cut the scourers and mix with scourers. expanding foam works but itsnt very pretty and eventually the fuckers eat it too so will need checking but that particular hole is shoddy decoration and not finishing it properly. put something temporarily to block it and get the radiator pipe collar .. make sure you take the diameter of the gap and the pipe although the pipe size is probably universal standard..just to be on the safe side.

you break not bread. though they are tough..probably strong wire cutting siscors or secateurs (garden trimming scissors)

i fucking hate mice.

Agree with wire wool. If they are using the hole already they will be even more determined to continue. Once you put them off you can replace it with something less obtrusive such as caulk or timber.
You would also do well to stop them getting under the ground floor in the first place as they can chew cables and pipes. Check any air bricks and gaps under floor level including within steps and decking.
As well as mice that will let a lot of cold air through from under the floor in winter. We spent a lot of time insulating under our ground floor to prevent draughts.