You are right he needs to see a vet NOW.
There are animal charities if you are on a benefit. contact the PDSA as has been said.
If you get no joy pm me and i will give you a cat site that maybe could help.

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Grandma to Jinja Dog, Mum to Tilly the Cavalier, Tattycat, Moomy, Choo, Sonic, Niven Mc Twisp and Lawna the rabbits and 1 guinea,17 budgies, 4 Cockatiels, 8 Goldfish.