The delivery price of £525 seems quite high - I guess that is "outsourced" and they have a management fee added into it, or something.
I always prefer a boxspring base with a good quality spring mattress on top.. whilst it may cost more than some beds, it is an investment in your health and lifestyle, and will probably end up working out to be the same cost as a cheap bed over time (you will likely have to buy 2 or 3 cheap beds in that same period of time)
I ended up purchasing this bed last year http://www.superiorbeds.ch/burgess-natural-bed/
- really pleased with it.. I always thought I liked "hard" beds, but when I got this I changed my ideas. It seems like the bed industry has moved on since I had previously bought a bed!!