One of the females reported on the GM forum had colour tags, evidently from a Dutch marking system. See the Photo Gallery on their main site http://www.manchesterbirding.com/
Was there any sign of colour rings or tags on your bird, Dave?
Forgot to mention - this is for Nick Fyldes - it looks as though you have tried to register for the forum but there seems to be a problem with your email address. Can you email me at jimormerod AT yahoo DOT co DOT uk and I'll try to sort it out.
Another message in case Nick Fyldes reads this: Nick - I've activated your account, so you should be able to log in to the forum using the user name and password you set up. Let me know if you have any problems.