Now that's just being disingenuous.
You know as well as I do that the only fields that AirNav are populating (apart from the photo links) are registration, type, serial number and Mode S code - information that is, to all intents and purposes, in the public domain (if it wasn't, presumably you wouldn't even be attempting the task).
How many enthusiast societies and websites that publish this kind of data, for UK and other aircraft, do you think have been prosecuted by the CAA and its equivalents ?
All Mode S codes issued throughout the world are technically the property of the issuing registration authority, so following your argument to its logical conclusion would mean that nobody is ever allowed to publish any tieup data without express prior permission from the relevant organisation.
Granted, if AirNav were planning to buy and then redistribute proprietary information such as owner names and addresses, airframe hours, C of A expiries, etc, then clearly the CAA would not stand by idly, but nobody is suggesting that.
So I stand by my original point - trying to collate a UK Mode S tie-up database while ignoring the availability of official data is like cutting the grass with nail-scissors when AirNav could have bought you a lawn-mower :-)