Thanks everyone for all your great support and help! I'm starting to think it's anal glands because Ollie seems to be nipping at his bum a bit and having runny poo. I'll ring the vet tomorrow as today is a public holiday!
Ollie still scratches his collar a lot! His had it for 2-4 weeks roughly and its on all the time now. It's quite scruffy looking at the moment! He also scratches his ears quite a bit too I'll bring this up at the vets too.
Once again thankyou everyone