Sign up to NielsenIQ and they'll send you a free product scanner. Use it to scan in your grocery shopping from home and they'll give you rewards for doing so. In-store and online shops can be scanned. How good is that!
There's loads of different rewards to choose from. You can get big items like TVs, iPads and watches or you can go for the simple option of vouchers at all high street stores. I'd definitely recommend you sign up. It's one of our top tips for making the annoyance of shopping that bit more bearable.