Microchipping is no guarantee that your missing cat will be found, but if it is found and scanned, you will be contacted. Too many cats are found un-chipped and eventually re-homed because nobody knows who they belong to.
Whether your cat is indoor, outdoor, young, old, pedigree or not please get them chipped and neutered!
Note: Microchipping is also available from your vets, some rescue organisations some groomers and other private implanters. The cheapest, as far as we are aware, being the RSPCA at £5 if you make an appointment at the Norwich and Mid-Norfolk branch at Longwater.