Just in terms of escaped falcons it is worth being aware of the Independent Bird Register
http://www.independentbirdregister.co.u ... Found.html which provides lists of recently escaped birds (if registered with them) and a place to report found/seen birds (if you have the bird or have seen a ring number etc).
In terms of identification escaped falcons, the majority of falcons produced in captivity are hybrids these days and trying to identify them as anything else is probably over-ambitious.... If interested in escaped falcons I co-wrote this paper (
http://www.int-res.com/abstracts/esr/v14/n3/p243-257/ - paper is free open access) which, amongst other things, used evidence from registration of birds under Schedule 4 of the Wildlife & Country side Act to document the numbers of registered falcons which escpaed or were released to the wild.
Vin