I’m try to download the ELO gig, but despite being able to watch this on iplayer, no episodes show up when i search.

I’m guessing this may be because this is a red button show that has not been broadcast yet?

If you can play from here https://www.bbc.co.uk/sounds/play/m0009yzz

open the PVR
go to the search Tab,
paste that url in the Quick URL box
click on the Record Button below it.