So, I went for my test today - the plan was they would use the ultrasound to locate the relevant lymph node(s) and then insert a needle so they could do a biopsy.
But they couldn't find the relevant lymph node. The doctor and the ultrasound technician were both looking at the scan from a couple of weeks ago and then trying to find it in my actual armpit area and they couldn't find anything.
Presumably if they can't even find it anymore that's a good sign? At least it meant I didn't have to get the needle so that part was good. And it was kind-of funny.
The doctor said I should go back for my follow-up with the surgeon and ask him for another referral and then they'll try another ultrasound around the end of January. So that doesn't help with my aim for it all to be over and done with!
Anyway, my general optimism/disbelief in badness happening to me is swinging back into action so I expect it will be ok. It'll just take longer to confirm that I was hoping!
Thanks for all the support and encouragement everyone, I really appreciate it!