Several weeks ago I applied to get money off vouchers from Dietary Special foods. In the last couple of weeks I have received two vouchers for £4 off. Hurrah. I eat their gluten-free breadsticks and rice cakes, so I will be buying more of those with the vouchers. Here is how you can get these vouchers. You have to register with them on their website http://www.dsglutenfree.com/. They will email you confirmation of registration, then you have to wait weeks for the guide and vouchers to come through.
So, if you eat any of their foods, it is well worth it to register and get money off. You can save a bit of cash, esp as I know that a lot of free from foods are expensive.