thanks for your help. He hasn't lost his appetite/weight and his gums are a normal colour so will try that vomiting medication you suggested.
Would I be able to get that from somewhere like pets at home or would I need to actually go to a vets to purchase it over the counter?
just an update on the cat being sick situation (in case you get a similar thing in future).
I strongly believe that the sickness was being cased by an additive or something else in the Whiskas wet cat food (sachets) I was feeding him (this applies to all flavours, not just a specific one)
His whiskas ran out, and he has been fed kite-kat sachets instead this week and hadn't been sick all week.
As a test (and this might sound harsh but I think it confirms the issue) I fed McFluff a pouch of Whiskas last night, and when I came home again today, the vomit was back.
Just thought you might like to know in case you get another person with a similar problem in future.