They are all proven to work, most have been established for years with a decent payout record.
Swagbucks is a great site, its one that has so many potential ways to earn, that it is easily possible to make £10 + a week depending of course on the amount of time you put into it. Just an hour a day on swagbucks will make you £25 a month simply by doing a couple of surveys, searching or by doing other tasks on the site.
GiftHulk is a GPT (get-paid-to) rewards website. Members can earn Hulk Coins by participating in various tasks, and coins can then be redeemed for a wide variety of gift cards and cash options.