Hmm, 6.25pm is a little early for the evening Glasgow or Edinburgh flights, and a little late for the Inverness (or Belfast) flights. I suppose it could be either of the latter two, with a delay, perhaps?
Re tracking, there are some online websites that purport to do 'live tracking' - Google will turn up tons using the terms 'flight' and 'tracking' -but as you've no doubt already discovered, they are very US-centric, and where they do cover UK flights, they'll only be transatlantic ones.
You could have a look at the ACARSD website (
www.acarsd.org) which purports to retransmit ACARS info on the web (either via a standalone client app, or via a web-interface), and doesn't need you to have a radio. Obviously, this will only cover traffic which is ACARS-fitted (by no means all), and it's probably a bit esoteric, though it is possible to hook it up to another program (PosFix, I think) which will display a dot on a map, but only when each plane sends another ACARS message with position data in it. In short, rather 'sketchy' coverage, alas.
Can't think of anything else, sorry... and can't help thinking that el cheapo airband radio off of Ebay or a car-booty is probably your best bet, even though it's not your desired solution.
Regards