Most franchised dealers have a discount scheme in place for new cars - the % discount depends on model, manufacturer etc. Usually from 8-15%.
(This is a seperate deal from tax-free/tax-paid sales.)
Nearly new, you'd be better off looking at pre-registered if you're buying from a volume manufacturer as they're often a bit cheaper than a fully discounted new one - again it depends on model.
Also, you may get a better deal if you or a member of your family works/has worked for a big company/organisation such as BT, Royal Mail, Police, Civil Service etc. Similar discounts, but you may also qualify for schemes such as 0% finance, free insurance, cashback, deposit paid etc.