[bobplum]

one very cheap and quick way is to buy EPDM (rubber roofing material) about £6 per sq mt and lay it in the van with extra to go up the sides

[hasti]

If you can diy a fiberglass floor I'd go with that over protectakote
something like one of these roof kits
http://www.fibreglassdirect.co.uk/roofing-materials-and-kits/roofing-kits/5m-fibreglass-roof-kit.html

will do that with my next van
My current peugeot expert has protectakote that's worn a bit so am going to re do it with a 1 Liter tin and put one of these mats  over it so it doesn't chip so easy
http://www.ebay.co.uk/itm/151317621549?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2648

I second that, Fiberglass is a great stuff, i have had mine for over 2 years and still going strong.