Cheapest I've seen for this on blu ray.
Also there are some bank holiday codes if buying something else with it:
AUG10 £1 off £10
AUG20 £2 off £20
AUG40 £4 off £40
So if buying other items too, you could get it even cheaper!
Also don't forget if you have car insurance with morethan you can get 7.5% using http://more4me.morethan.com/