Space, I can recommend you Express National Carriers. They're based in Long Lane, are very reliable (at least the few times I used them), and you always have impeccably clean cars and courteous drivers.
Downside is you have to call them and can sometimes have to wait for some time before they can send you a car. Their number is 020 7403 3333.
Another option is the well-known Addison Lee. They're more expensive than ENC, but have more cars, so if you're in a hurry it's a good choice as well.
No connection apart from being a satisfied customer.
Being a regular for years from elephant cabs I phoned a few weeks back for a cab from bartholomew street to surrey quays. I was horrified to find out the fare had increased to £9.00 i told the driver to phone the office to check as i am sure that was incorrect, the controller told him that was the correct price. The entire journey took 5/6 minutes.
I told the driver that was the last time i would be using the company..phoned another company to get home, loaded with bags...journey cost £6.00!
I am now using express cars and they are brilliant , nice new cars and far cheaper!
addison lee man myself...txt you to give you the car details and when the driver has arrived...always clean and on time...as cheap as a black cab with the conveneince of it waiting for you outside your home.