So if I go for a new system and the tank is to be fitted (I guess that means bolted to the chassis) who does it? I mean if you're not too near anywhere selling them.
Do it your self with a buddie to help you, So much cheaper.
Go to a metal fabrication unit and get them to make you up 2 metal straps to fit your tank, has to be way cheaper than £87 that is being asked for 2 metal straps.
Before you go there pop underneath your van and see if the tank sits across the chassis? if it does then thats the best fixing points, if it doesn't, then get the same metal fabricators to supply you with some wide flat steel, (let them know what its for) if you can get it, so it will have both bolts fitted to the same lenght of flat steel, so much the better, this will spread the force through both bolts and not just one bolt.
You then need to buy high tensile steel nuts, bolts and washers, washers fitted to the tops of the bolts and star washers fitted on the nut section.
Always tighten the bolt and not the nut, if you tighten the nut then the star washer will create a groove in the plate, were as if you tighten the bolt, it will pull the star washer tight and create dimples in the plate and stop it vibrating loose. HTH
PS
If your Tank does fit across the chassis, give me a shout and I'll tell you the correct procedure on how to fit it to the chassis.