Thanks Jeff - it is model 272ES, SP AF 90mm F/2.8 Di macro 1:1 for Sony a-mount.
Got the lens back yesterday evening by courier from Intro 2020, the Tamron agent in the UK. They had dismantled the lens, cleaned the lens, replaced the mount, and then tested before returning. All works fine now - phew! I'm not sure whether I should be pleased that Tamron offered a 5 year warranty and that Intro2020 repaired and returned the lens so efficiently, or if I should be disappointed that I had a lens fail after 4 years
Nex 5, Nex 6 (IR), A7M2, A99 and a bunch of lenses.