Hi - I had rabbits for many years and the most recent ones I bought were also from Pets At Home. Depending on the ages of the rabbits when bought, you cannot always tell their sex. My female rabbit ended up having just the one baby, stillborn, and I was told by the vet that this may have happened as she was so young herself and didnt know how to look after the rabbit pup!
I would recommend castration for the male as this will also stop his spraying if he feels someone is in his terriotry where his "mate" is concerned. My poor white female was constantly receiving this "stamp" off her mate when they used to play together in the garden.
Good luck xx