Goodness sorry you haven't got total answers but it's something that they are saying it's not very nasty. They have to be cautious though as can't do definite tests til get it out .
I can help a bit on Wellington v rnoh as had one op in each.
Wellington - pros- not likely to get bumped for another op, lovely rooms and great food ( not to be sniffed at if you are in for a while). Senior neuro nurses are fantastic. There is the most fantastic specialist pain consultant working there so your rehab issues (ESP given history on addiction) would be well covered.
Cons- most of nurses are bank ( ie temps) so mixed quality ( they messed up my pain relief til consultant yelled at them). The icu isn't as high tech or well staffed as rnoh so in terms of operating theater and after it's not as good.
Rnoh pro- the best nurses, drs in theatre and icu .
Cons- it takes a lot of emergencies so could wait or ce bumped. Some of private nurses not great (but not to same degree as Wellington), the rooms/food are ok but not quite as nice as Wellington but lots of good places for family to get supplies/take away locally.
If it was me, if I was dead scared about op then go to rnoh . If you are ok on this and want a more comfortable/well looked after stay then go to wellington.
Does your consultant/ surgeon have initial c?