When I saw the title of this thread I thought it was cat flu and your post confirms it for me. Until you can go to the vet to get proper treatment I would bathe his eye with the water (cold!!) from a teabag.
And yes deffo get insurance. However this illness will not be covered by it as it will be seen as a pre-existing condition.
The cream we got from the vets for my mum's cats cost around £15 by the way but this obviously varies from vet to vet
