I’m a terrible hoarder and have at least 2 old PCs sitting about the house which will probably never be used again.

What do I do with them?

Go to the tip and they should recycle them.

Wipe the hard dirve first though by leaving in a bucket of water

to add to the OP – I’m aware you can give then to charity, which would be my choice, but to embellish the original question, what do I do with the hard drives containing personal data (despite being erased I know it can be retrieved if required)?

Coffee table?

It’s a problem. If they’re working, places like local youth clubs might well be very grateful for them. I got rid of several CRT monitors a few years ago by donating them to an after-school club. I couldn’t pay people to take them away otherwise, but the club tore my hand off for them.

what do I do with the hard drives

DBAN.

I personally take a drill to the hard drives, coupled with a big hammer. Very stress relieving.

I donated a load of computer parts to my old workmate, who butchered them for working parts, and recycled the rest. Have Freecycled one as well.

Normally DBAN the hard disk and stick it on freecycle.

I usually end up giving them away to people, Freecycle (or Freegle or whatever the hell its now called) is a good one. Offloaded a couple of old systems recently to people wanting them for their kids for school work.