A benign meningioma.
Essentially, if you had to pick a type of brain tumour to have, it's the one you'd choose. And it's what I've got!
Future discussion will take place with a radiologist about whether to treat now or monitor and treat later if necessary (there are good arguments either way) - but it's all suddenly gone very relaxed and non-urgent (growth being ~1mm per year).
I'm really looking forward to a good night's sleep tonight...the 27 days since the 'you have a brain tumour' phone call have been somewhat intense!