From what I know, and if possible,
keep the colours without shades, as the simplest process is a machine cutting the letters out from sheets of coloured vinyl. If they have to print shading onto vinyl, it will increase cost.
Get him to superimpose his design on photoshop or other first, as they have a design cost charge, it also allows him to email what he wants, on an image, and get a definative cost.
If possible, avoid lettering or logos crossing over folds on the van. This is a specialist vinyl and adds cost.
Don't bother with fax or email addresses......useless clutter.
Sorry I can't recommend a Dublin supplier.