How the hell would a cash for bicoins meeting go down with 10,000 gbp being given over? I've seen people selling for cash with massive top limits...
what the hell? dodgy no?!
Big purchases like that, you better do at a place like a bank (the irony) or at least a place with many security cameras and or security guards.
If you talk to a banker that's friendly, they might let you use their lobby or even a desk to conduct the transaction.
You might even consider renting your own security guard for the day to make sure nothing happens
Money spent on security is money well spent.