What to do with an injured stray cat
If you find an injured stray cat it is important that your first point of contact is the RSPCA. The RSPCA can be contacted on 0300 1234999. They will advise you to take the cat to a vet if needed. Only when they have advised you to take a cat to a vet will they provide a log number. It is important to obtain a log number before taking it to a vet. This log number will mean that the RSPCA will contribute something towards a cat's treatment.
The RSPCA will not issue a log number to a vet, only members of the public ahead of the cat being taken to the vet.
Healthy Cats
If you find a healthy cat it may live locally, they do roam and some cats 'adopt' several owners receiving a bowl of food from each. Don't be too quick to pick it up and take it from the area that you found it. Feeding it may well prevent it from returning home. You can put a collar (quick release safety collar) on a cat with a note asking the owner to contact you if you feel that it may have a home. Alternatively you can have it scanned to see if there is a microchip which will enable contact to be made with the owners.
If you have a cat that is working the system and getting fed elsewhere, you could consider buying a 'Please Do Not Feed Me' collar!