This is the 5cm Deluxe version. The normal Slientnight Impress topper is 2.5cm.
The same shop is selling the King size on Amazon, but with a £4.95 delivery charge. and the double version on Amazon has gone up in price.
I think it's a good buy, as I was about to buy the 2.5cm double on Asda Direct for £45 as I couldn't find the 5cm version anywhere apart from Tesco for around £95.
Plus this seller is the same supplier for the Groupon deal to get the 2.5cm one for £49 + £7.99 postage.