I have been signed to yougove for a couple of years now and they are the best. They really do pay out, but it takes a full 2 years to reach that �50 target before they will send you your cheque, but they are genuine. You receive 1 or 2 surveys per week, sometimes they are only for prize draws, usually 50p each, sometimes 75p each.
The other one that I am signed to is Ciao, but they pay very little money, something like 10p per survey, take ages to fill, and on many occassions afte you have completed a few mins of survey, they tell you that you are not eligible.
Unless you are really desperate for cash and have a lot of time on your hands I would avoid Ciao as you are no more likely to get paid a fiver a year with them.