Thanks for the suggestions everyone.
When I first connected the pot, the wiring was as per the schematic (and therefore incorrect). I has this corrected in the first 10 minutes of operation, so it is now wired the correct way. Unfortunately this didn't fix "this" audio problem .
The fact it is getting hot sounds like its not very happy. I will double check the values of the surrounding caps and resistors are correct, and then order a new TDA2822 I think. (Unfortunately I don't know of a local supplier here in VK land.. I might have to wait for some to arrive from china.... :/ )
Unless anyone has anything else to suggest?
@Raj vu2zap - regarding the R51 change - will this have any impact on TX audio? or will it change RX only??
Thanks again you all.?