Having worked both sides of the fence both in the office and in the car, I have dealt with the "Liverpool" company (cabfind) 4 or 5 times, there are two or three onward travel companies around that deal with the bigger taxi companies. The best one was one that was based in the US, I called up one of their guys at 3am asking if they knew where their passenger was, while waiting, as you do, you shoot the breeze and ask how their day is, to which he replied he was sitting in his house in Texas, it was 95 degrees and he was about to go out onto the porch to have his burritto and a cigar. The other company that we dealt with was Cabfind which is central Liverpool number that a lot of people talk about, IIRC they were taken over last year. From a Dispatcher's side, they can be a pain in the backside especially when trains go off around school run time and all your drivers are on school runs, (Cabfind used to be really strict that if you couldn't drop everything for them when they rang they used to look elsewhere, they changed their attitude when they had been through every company in the town and realised that at school run time, no taxi company will have 20 cars available to send straight away).
From a driver's side, they can be a godsend, it isn't the first time that I have been about to go home of an evening because the pubs are quiet and had a freight driver job although it did annoy some of the drivers at Westbury rank when I drove past them without a pass, Cabfind used to do the runs to Manchester for a well known now cancelled daytime TV show.
The issue we had was that sometimes it could take months to get paid, Cabfind would drag their heels as they hadn't been paid and at one point my friend's business nearly went up the wall after being owed 6 figures by then.
I know Cabfind used to have a lot of the Firstgroup work, so Scotrail at the time, GWR etc...