Distance selling regulations have you covered, you have 6 months from date of purchase to take your money back on anything you purchase without viewing.
I have just had to remind Holan of this as they are not responding to my emails and I have not received my bars after a month of waiting and they have now set my order status as COMPLETED...
If you are unsure though just contact trading standards and they will set you straight, they informed me of these regulations when my missus purchased a problematic car which the garage wasn't willing to repair, we contacted our bank, took our money back and a week later the garage realised and came to collect the car, we did not even tell them we was doing this
