The Cardiff shop is definitely closing.
I went into there yesterday and there's posters all over the place saying "Closing Down - 50% off all books". There's nothing in the windows and there's a lot of empty shelves. I bought two items - one military book and one DVD ("Flying Scotsman" - the film) and paid about £16 for both.
I asked when the closure had been decided and I was told "Just before Christmas". There was a sign suggesting that people could make comments about the closure to someone at the head office, but I didn't take any details.
I have heard that the rental costs in the Morgan Arcade (where the shop is/was located) are very high, so it's no surprise that it's possibly not viable. I visited the shop quite often, probably every couple of weeks, and there always seemed to be quite a lot of people in it, but whether or not they were buying, I don't know. Certainly, I didn't buy every time I visited, so I suppose I must share the blame!
I'm not sure when the shop is closing, but it can't be very long judging by the lack of stock on the shelves. It's a great pity, as there aren't many good bookstores in Cardiff, and I do like a browse to see what's available. Having said that, I do use the internet to buy most of the books, so as I say, I probably didn't help.