I've been on Gettaxi for about 3 years now.
There's about 4000 of us on it in London, and I can see from my tablet, they've been recruiting in Liverpool, Manchester and Birmingham too.
Believe it or not (you get access to pre booked orders on their tablets) I've seen a few jobs booked by account holders in Edinburgh over the last year, obviously Acc holders from London do travel and want to use the same app wherever they travel to.
The system has its faults, but overall its bagged me numerous trips to and from Heathrow, and has some good accounts that have found us to be far more efficient in both service and costs compared to the sat nav mob and their non English speaking drivers.
It suits me as well as I only pay a pound or two for each job depending on the final fare costs, and its free at the weekend.
Punters are the biggest failure, wrong geo locations, cancelling after you've accepted a ride, putting wrong destinations in so your 'cream' ride turns out to be a rtfc after driving for 15 mins to reach the 'cream' job, but overall punters and drivers like it.
I understand there's established apps in Edinburgh, but I'm also understanding if you're not on a radio circuit its tough tittie, and you have no access to a circuits app as a street car? I believe it costs thousands to join a radio circuit?
Situations reversed down here as circuits cant get enough cabs ..... I could join Radio taxis for £6 a week and 10% a job, and they hold the London Underground account!
Get Taxis UK registered office is in Highgate Road, London, I have no idea if this meets the licensing requirements of Scotland?
Give it a try.