Update: after procrastinating for a while, with my thorn-damaged tyre on the spare (holding full pressure), took it into my trusted tyre dealer yesterday, fearing the worst.
"Oh yes - that can be repaired - it's almost a new tyre - you don't want to scrap that! Goes away on Wednesday, comes back the following Wednesday: £30 +VAT"
Meanwhile: he's lent me a Michelin of the same spec to keep me going (no charge). My tyre will be re-vulcanised, and come back "as good as new".
That's what I call service
