Thank you so much for your kind replies. There is such a store of compassion and humanity here. I am incredibly grateful.
I had a counselling session yesterday with Macmillan (the UK cancer charity, as I was diagnosed with PTSD from all this). We talked about this new lump.
I feel that, on balance, it's quite likely to be simply scar tissue. Fortunately, or UNfortunately, I am a person who needs "evidence" - facts and figures. This is a blessing and a curse, and I know it can make my thinking rather rigid and times. Sometimes it stops me from feeling as hopeful as I could feel.
Although I don't yet have the "evidence" my mind craves, in the form of the biopsy results, I am FORCING myself to at least be realistic, if not 'hopeful', it is highly likely this will not be a recurrence of the cancer. It is more likely, realistically, to be scar tissue.
So that's my survival plan for the next couple of weeks

Main thing is, I am feeling generally a little more well, a little more energy, more confidence - and being back at work has helped me with these things. It has stopped me brooding at home, dwelling on myself all the time, although I think cancer makes you a bit like that at times....
In my job, I have 8 hours each day where I *must* think about 12 other people, and the other nurses and support workers I work with. Having the thinking pointing outwards instead of inwards is VERY healthy!