Seeing as i only fill up with fuel at Tesco, i get to use my clubcard and so have loads of points. They're worth £65 in cash, but you can convert them on the tesco website to rewards, which are worth 4x more.
So... i've gone for hotel vouchers, giving me £260 of vouchers to use. So i've just booked 4 nights at the Hilton in Kensington, London over christmas day, which should total £490, but its only costing me £230...! How cool is that?! Propper bargain!