It clearly means all prices are exclusive VAT, so you have to add VAT.
Companies always calculate prices exclusive VAT, because the VAT has to be paid by the 'end' consumer. On an invoice to comsumers and companies 'inside' a country (eg. within the UK), VAT must always be added. On an invoice between companies in different countries, there's no VAT.
(Thats the Belgian law, but I think it's pretty much the same in the UK)