Thought this may be of use to someone. Marshall Ward (&choice, additions, littlewoods direct ) have a single, double and king size bed on sale with free matching size mattress.
Go to one of the sites and search for Valentino , the one for sale is in black though. It shows the king size as on sale for £67, but if your a new customer (or can order as one) and use the code ZG430 it will give you £30 off a £60 spend, (so if you get single or double you will have to add small thing to take price over the £60.
I ordered mine from Marshall Ward, but apparently the code works for the other catalogues too. I also paid by debit card, I did not open an account to use this voucher, and have had my order confirmation etc come through for the grand total of just under £42.