I work at B&Q too, I only had one interview, I don't know what kind of post you're applying for, my experience was for checkouts, its different for other departments. My interview was with the Checkout Supervisor (well, one of them) who was really friendly, its a standardised interview unfortunately I can't remember much of it, it was very scenario-based, things like "Think of a time you have had to work as part of a team," and then there would be follow-up questions on the scenario you brough up, other ones I remember are "Think of a complex decision you have had to make" and "Think of a time you were involved in some DIY" (Try and think of something other than, 'i helped decorate my bedroom, apparently 90% of people say that). I think there's stuff about 'what is good customer service' etc. aswell.