Managed to source new drivers and successfully repair, so thought I would leave these breadcrumbs for future searchers. The drivers are Tang Band W3-1401SC, which Multicare sourced for me. They were £20.03 + VAT each, plus postage (£15). They look a lot like Tang Band W3-532SQ but the F80 cones are aluminium, whereas the others are some kind of plastic.

Riding on that wave, I purchased an M80 for one of my nieces, which has a bit of a hum, but will post about that separately.

F80