Thank you all for your helpful replies. 🙂 I took him to the vet yesterday and showed her some videos I’d taken so she could see his behaviour.
She thinks his hearing could be deteriorating and that noises aren’t sounding the same at the minute which he’s finding confusing. He had a good check over and there were no other problems, thank goodness.
I’ve got Yucalm to try out, a DAP collar, and we’ve moved his bed into a quieter room away from the hustle and bustle of the house. He’s starting to seem a bit happier already.
it’s very useful to know about slight changes upsetting greyhounds as now I’ve had a good think about this, there are quite a few things that have changed. Heat, as mentioned, which it turns out is quite noisy at night. Also, a new bread maker we put on at night which clacks for a couple of minutes quite noisily! He’s probably been petrified!
Thank you again - what a useful website this is!