A few years ago their prices were amongst the best, so it would be feasible to use a few vouchers at once like this, but nowadays, not so good. I think they almost went under because of some legality and since getting new managers, they've turned into this sorry shower.
I have used the £2 to get the price down on American Gangster Extended tin case edition. They are currently the best priced on that and Atonement. But the latter is only a single disc bare-bones so will be in the 4.99 bracket everywhere in a couple of months.