A kit for less than £30 - I'd be a bit worried about the quality of the parts to be honest. A cheapo belt would be less likely to last the recommended 72k miles interval change. It would be good if you could find out the make of the belt. Better quality tensioners are quite often a bit noisy when they are changed at the recommended times - a poorer quality one may not last that long. It's your choice of course, but very cheap is rarely very good.
Les.