I think my cat Harry, has been in a scrap today (we have a lot of cats in our neighbourhood, at least one of which is a big bully ).
My question is, what is the best thing I can clean the wounds with, salt water or similar? They are on his face so it will prove difficult I guess. I'm aware they can become infected and therefore necessitate a trip to the vets.

Salt water is fine.
What you need to worry about is the wounds you can't see under all the fur, if he has been bitten he will almost certainly develop an absess or two, typical sites are round the neck and in the armpit.
Hope he is okay.

Also worth checking for scratches on his belly and even the odd bite on the bum!

Yeh mine have sometimes had bites to the back of the thigh as they are trying to run away. The puncture wounds are incredibly hard to spot, my female oriental cat was bitten a couple of weeks ago and the only reason I knew was because I saw the blood on her neck when she came in. A day later I couldn't find the wound despite her having really short fur - the vet did though when he followed my directions

Thank you, I shall keep a close eye on him in the next few days