Oh yes they do, I often use my Camping and Caravan Club membership alongside their discount card , it gives me an extra 10% saving. Also they will price match any item that you can prove is cheaper elsewhere. It has to be exactly the same though, this includes colours.That's correct; for example, Go Outdoors don't allow a Blue Light card discount to be combined with any other discount beyond the normal membership price.
That said, you can occasionally get lucky. I've just picked up a new 3-in-1 jacket from Cotswold Outdoor. It was already down to £120 from £150 and the Manager gave me the additional 10% Police discount on top because they had to order the item in from their London Covent Garden store and it would take a week to arrive (Cotswold's count both BF and IE as Police for discounting purposes). I got another £12 off, which was a bit of a deal as far as I was concerned.