UPDATE: I got about a dozen replies to my advert and after a few casual interviews in coffee shops I selected two girls and a man with whom I thought I will communicate well. I've had a few drives with them and everything has been fine; depending on how far I was travelling within the 20 miles radius I cover, I ended up paying between ?20 and ?50 per appointment for the driving. Unfortunately, I'm not getting much work - about 1-2 clients a week only - and therefore didn't have much work to offer the drivers, which I think they are a bit disappointed with, but there's nothing I can do about it.
Consider also that to about half the bookings I've had since then is's been convenient for me to travel by train or bus, which I did, as it was obviously much cheaper. There's also been cases when I had a same-day booking but none of the three drivers was available (of course, since they can't make a living driving me, these people have to go on with their lives) and I declined clients or in a couple of cases managed to travel there on my motorcycle. That was a bit awkward, but it worked out well in the end. In both cases I managed to find a pub or restaurant with a toilet room nearby and get changed before meeting the client - but this arrangement also meant I was carying my big rucksack with me for my motorcycle jacket and other clothes in.
I'm now preparing to get my car license. I've already got the car, insured and all, and have hired a casual accompanying driver to practice with me every other day. My driving is improving greatly and I hope that sometime in August I will finally have my own transport.