Modifying your caravan - what have you done? Tips?

We've just bought our 1st van - a 2002 Swift Challenger 5 berth in great nick although the dealer was a bit of a cowboy. However, to my eyes it needs a few additional modifications and as I fit kitchens and bathrooms for a living it shouldn't be too much of an issue to do so.

First up - electrics - The van only has 3 internal 240v sockets, so I'm looking to install at least 2 more, to cope with the endless chargers and gadgets that a family of 4 have - my only challenge is finding the right "Clipsal" units now they're discontinued! Also, a couple of waterproof 12v lighter sockets into lockers either side, to power a cool box in an awning if "off-grid" and provide an easy connection for a tyre compressor if required.

Second - water - the dealer helpfully supplied a "new" external pump which turned out to be a whale unit which had been stripped of all the pumpy bits and we've now fallen out completely over a dangerous tyre and a few gremlins I've had to sort out myself. I can easily retro-fit a pump into the casing/hose, but is an internal pump better? A submersed unit outside is presumably silent to the occupants, but is an internal unit really that noisy? Also do external one's get pinched?

Gas - The van has space for two cylinders, but just one hose/regulator. Does anybody use a tee and two regs to connect up both or is this overkill? 

Any tips or good ideas? Once the van's out of warranty I imagine many people must tweak them to suit their individual need - any good suggestions?