Soupy, that's brilliant, thanks very much,
certainly given me some ideas, I may still go with a bespoke baffled tank (in case I decide to keep the height flush with the sides plus it gives me the option of having fittings where I want) but at least I have something to compare the price to, sounds like I could create space for 400 liters. Yep a hard top, will be dual purpose with the idea for the vehicle to have space to be an overnight sleeper for mountain bike trips away etc
cheers
Simon