Jeeze what did you get lol... I was quoted £42.50 all in for a brand new diesel battery (dearer then petrol batteries) from Europarts in Moreton. I think the dearest place was quoting £68 lol.
Halfords are absolute rip-off merchants. In the end I got myself a second hand, but practically new one (still in packaging etc) from the scrappy for £15 lol.
Btw, you can get away without the battery being secure on the MOT, ive had an advisory for it twice lol.