Thank you for that helpful advice and input.
We have discovered that yesterday when Parsley had his ear cleaned the (junior) vet nurse who did it mistook some exposed white cartiledge for pus and squeezed rather too much to try and get it out :shock::shock: and then didnt realise that not eating very much was a HUGE pain sign for Parsley (who will eat a bucket of greens a day even at the vets).
He has been in again today and has proper clean and some ketamin to go with it - he finds his ear pinnas very sensitive and always reacts badly to even small swellings in them (as opposed to the 2cm diam ball of puss in his head which he totally ignores:shock
The vet is actually happier with him now than she was a couple of days ago when she was concerned the infection in the bulla might be coming back (after removal of bulla this can happen and it swells in other places) as we had pus low down in pinna/head area . . . though he still has a worrying swelling in the lymph node and has not had his bloods redone to see if anaemia any improved. But one thing at a time . . .