Thank you for the welcome and for your helpful thoughts and advice about foam insulation, Phil.
Bloody hell £1,200, geeeeeeeeeees, if you are talking about MPI there prices have gone up enormously. If you contact Jake Clarkson @ One Insulation
https://www.oneinsulation.co.uk/, mention my name Phil McDonald and I hope he will recall giving me a special price of (I hope this senile old brain of mine recalls correctly) only £12 per sq. mtr.
I can assure you that the quality of their work is quite literally head and shoulders better than the job done on my van by MPI, One Insulation is as smooth as a babies bum whereas MPI's looked as lumpy as lumpy could be and it resulted in me having to spend an enormous amount of time cutting it back.
The foam that One Insulation use comes from America and it is 100% closed cell as it has to conform to all the building regulations stipulated by the government. Their main work is spray foam lining roofs of old houses, lining boats, lining storage containers etc.
The difference between Ones and where I had mine done is that they are constantly checking the temperature of the mixture, and by constantly, I mean about every 15 seconds!
As for the ribs yes, to do the job properly they have to be filled with the foam, otherwise you will get damp inducing cold spots.
As for the flash point of closed cell foam, it simply doesn't burn.
With regards to your cable runs, in my build, I actually didn't have the floor spray foamed, instead I lay the 25 x 50 roofing laths that I used as batons on the floor and then fitted very tightly fitting Celotex (or similar) between the ribs. The reason why I did this is that I had 1 x long valley along the entire length of the floor and 2 x cross valleys into which I ran all my cables, water pipes and gas pipes. Then, wherever I have a plug socket or light I ran the cables vertically feeding them through trunking that I then recessed into the already sprayed walls. For the floor I then laid a 12mm marine ply that I had already varnished both sides.
One Insulation are as I said previously based in Sheffield and if doing vans, they normally will only do them at weekends, unless that is, you can get several people together at any one time to do their vans as well.
One final and very important point, you have to mask off all the areas that you don't want spraying, this is a balls aching job to do I can assure you, but it has to be done and it is also best practice to have some kind of curtain fully sealed to stop any overspray going into the cab area.
Another point worth considering is how to insulate the doors, my sliding door has a mixture of both spray foam and rock wool, but I didn't do the cab doors or indeed the back doors. With hindsight I would have insulated the cab doors but not the rear doors, the reason being that in my build, there wasn't any need to insulate the doors as the shower/loo room is fully insulated (using Cellotex).
If I can help in any other way, don't hesitate to do so.
Phil
ps. don't forget to insulate the area above the cab.