I think this reply by Paddy summarises the value of colour-ringing, please continue to report sightings.
Hi David, Many thanks for reporting your sighting - excellent shots too. This individual was ringed as a nestling at Stackpole Head on 5th July 2011. She was seen shortly after fledging near the nest site, and then not recorded again until October 2012 near Tenby. Your sighting confirms that she is likely to be resident in this area, and now she is old enough to breed, she will almost certainly be attempting her first brood nearby this Spring.
The colour-ringing scheme was started in order to gather more information about the survival of fledged birds and sightings such as this make an extremely valuable contribution. Thanks once again, Paddy Jenks