Richard, i've just bought an Avondale, but an Argente 650.6. On the side of mine is what looks like a white nut. The water pump is built into the van, underneath the seats in the front. Big black thing, capable of superb pump pressure. Mine is aalmost as good as my house water.
You will get a piece of hose with a thread and nut crimped into the end. You just unscrew the "nut" on the outside of the van, and screw the hose onto the thread that is their. Finger tight is plenty sufficient due to the way it seals. I was also concerned as i hadn't seen or used this system before, but after using it i must say it's deffo far superior to my old submersible pump.
How reliable it is i dont know, but it CAN run dry without damaging itself, unlike submersibles.
Mine was also a bit noist at first till it got the water through and air out, took an hour or two though.