OK, here goes:
Andark, on the A27 just by the Hamble, because they're only down the road and are jolly nice guys and girls. They do really good and fast drysuit repairs and although a lot of the time I ring up / pop in and ask "Have you got a <whatever bit of kit>?" and they haven't got it / can't get close for a price match, they are honest about it and do me some good discount as a regular customer.
Deep Ideas, because they have really gucci toys and they always send stuff faster than ought to be possible. And they put sweeties in with your order!
Dive Life, again because of good prices and good customer service for online shopping.
Force 4 chandlery, B&Q and Halfords, because duct tape, cable ties, string and bits of bungee are dive kit too... Aren't they?
Seriously though, Andark are not the cheapest for a lot of things, but I can walk there from my house (granted not with the twins for a fill) and I have cultivated a good relationship with them. Unless your LDS are a complete bag of knobs, it's worth supporting them. The alternative in my case is a 30 min trip each way for a DIY nitrox fill at the club. Which reminds me...