I sit my hose in one of these:
http://www.garden-goodies.co.uk/acatalog/Garland_Garden_Trays_G45.html Brilliant for catching drips. I have another of these trays that my 2 x barrels sit in.
The reel is secured by bungies that stop it falling over. In an accident the reel would be stopped flying forward by a big plastic tool chest and my Pure Freedom tank
..... just before the tank heads through the bulkhead of my Trafic and squashes me.
Do we all get too worked up by this safety thing. My local palleted goods courier company has shrink wrapped goods on pallets forklifted into their Merc vans and strapped down using ratchet straps through the existing interior load securing points. The bulkhead is their to stop you getting squashed, but getting hit from behind by your system is gonna be the least of your problems if you are travelling at more than 30mph imo. The inertia of your van + system hitting something reasonably substantial is going to do for you anyway. Or have I got this wrong (cue new thread about system safety)...