Textbroker is is good. I have worked for them off and on for about 8 years. You have to be hyper-aware about your grammar and spelling, but there is almost always work there and you get paid regularly. You can cash out at $10 and if you request pay Thursday you get paid Friday. I'm not sure what the cash-out threshold is for the UK version.
You can make more money on there by joining teams. Team clients will pay better regardless of your star rating. You can also set a 'price per word' for direct orders on your profile. This means that if a client sees and likes your profile, they can send you a direct order for an article and they will pay you the price you set. I have made some good money this way.
You have to put a lot into it, but once you get good at it, the pay is pretty decent. I write fast, and I'm a fiend about checking over my work, so I can make anywhere from $8-30 an hour writing on there, depending on what is available at the time.