Interesting! My neighbourhood in London (NW6 - not particularly upmarket) seemed to accept them fine... as well as most places in Central London.

Interesting indeed! My area has lots of tourists doing short stays, so I would've assumed that shops would be MORE open to accept all sorts of cash, but nope. Most places have notices that say they don't accept the £50 notes due to fear of counterfeits.

Shops can refuse to accept them but if you are using them to settle a debt; pay restaurant bill / taxi ride then they cannot legally be refused.

Yes they can. It means they can't sure you for not paying though.

[1] https://www.bankofengland.co.uk/knowledgebank/what-is-legal-...

Cue debate about if stamps must be accepted!