… and of course it’s done this in the wet bit of the summer.

The front passenger window is stuck open. From either switch being used all you get is a quiet but distinct click from inside the door, so the command is clearly getting there. I’ve tried the reset procedure to no avail.

Apart from making it weatherproof with lots of gaffa tape, is there anything else I should try before taking it to the local workshop?

Sounds like the window regulator has failed. You could try gently pulling on the glass while the switch is being operated, which might help get it back up, but it doesn't always work. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

When one of my rears did this disconnecting the battery for a few minutes (hard reset) got it working again temporarily allowing me to get the window back up.

It was, of course, the thing that never fails - as in the workshop had never had to change one before, no one had one in stock… the motor.

It is a common theme with Land Rover dealers! They’ve never heard of anything going wrong with their customers cars. They even put it in their workshop manuals. Sealed for life. Never have to do any maintenance on the auto box, diff or Haldex.