An update:
I left home on Saturday before the sparrows even considered anything, and took a pleasant drive down the east coast. The Icelandic volcano created great atmospheric conditions for a beautiful sunrise:
Anyway, got to Chris’s uneventfully to find a happy welder amidst a pile of steel. We hauled out the plan, which Chris had worked through and marked up the steel, with the vertical risers being pre-cut.
We (!) then cut the base, and welded that up quite quickly…
Right, I thought – I’ll be home tonight at this rate – fat chance!!
We’d had a discussion about how to actually fix this beast into the back of the 120, and had decided to pick up on the OEM tie-down rings. So on went some tabs, to line up with the floor holes.
We got the basic cube welded up (I say we, but one of us had to be the foreman, and one the welder – I’ll leave you to sort that relationship out

)
Then came the trial fit of the basic cube.
Spot the school-boy mistake
That's when the first bit of recrimination started – ‘But I thought you’d measured all this …!!’
Well – I had, but in my excitement, had never really twigged that the dog-guard would chew up an all-important 15mm of depth in the rear cargo bay …. Resulting in the base not quite hitting the tie-down anchor points at the back, and also catching on the rear door trim, which protrudes a stupid amount, really, at the top hinge-side corner, into the body of the vehicle!!
So a bit of jiggery-pokery later, removing the 'D' rings and slotting the mounts, saw the cube go in, and miss the rear door this time
So once I’d got over myself and stopped wanting to bin the whole thing there and then, we got down to the serious business of measure, cut, fit and weld. By Saturday night, we’d got the main unit complete, and collapsed for a well-earned beer and a great chicken dinner, and then to bed …
The basic unit is bloody strong, though! I can stand on it –
and so can Chris !!
Sunday had me woken to the gentle sounds of a grinder and welder in full song!! Chris was already hard at work in the garage (shame – he had to basically empty it so we could get in there to work… ;-) )
One of the components to go in was the fridge slide, and I’d envisaged it being mounted to some OSB or ply which would form the bottom of the bay it’s located in. We re-worked that idea to create a bespoke mounting system which is lighter but stronger – a couple of straps across the width and drilled with captive nuts spotted in to accept the fridge slide mounting points, and some M8 bolts right through. Piece of cake, and works a dream.
The 3rd battery was designed to fit behind the fridge – obviously now with no wooden base, we needed a new plan to locate and secure the 115aH Exide leisure battery, which is quite a large beast. Not having the wooden base to use caused a bit of a re-think, which Chris solved admirably by finding a piece of steel plate to weld in place, which resulted in a bespoke battery mount being created .. a work of art, and strong as a rock – that battery is going nowhere!
So lots of cutting, grinding, welding, swearing took place, much tea was consumed (well, some was, the staff left to go shopping, and to provide a great lunch, enjoyed outside in the sunshine) …
Final fitting:
I drove all the way home with it all fitted, and it’s absolutely noiseless, and doesn’t interfere too much with rear view … But I’ve been rethinking this, and would now do it a bit differently – I had to leave off the ‘outriggers’ as there was no way that the beast would fit in through the door with them on. Bit of a pain. Essentially I tried to maximise internal space, but that’s not really the right approach. I’ll now con Chris into spending a weekend actually teaching me to weld, and then play around making the Mk II version, which will be a bit different. Having seen how easy (relatively

) it is, that’s probably the best route. But I’ll go to France with it as is, and then decide.
So – to complete it, it’s going for powder coating, and I’ve still to fit the wooden ‘floors’ and get drawers made up – that’s it … I think. final pics to follow.
But a HUGE 'Thank You' to Chris for the hard work and organising - it truly was a lot of work, and he didn't complain much, really

I think this was the best route to follow, but it wouldn't have got to where it is without Chris selfless help, and hospitality - thanks, Chris - it's better than 'a bought one'

.