I think i can get round the issue of VAT not being supported by using the fixed tax rate of 17.5% (the current tax rate here in the uk) but on the module OrderTotals.ascx the is a reference to GetLocaleResourceString("ShoppingCart.Tax") which i am assuming is pulling in the default text of "TAX:" how can i change this to "VAT:"
In admin go to Location->Languages and then click on show stringresources for your language, there you will find all strings used in nopCommerce, find your string and change it.