In the real world I would go along with the advice given by your accountant as the general rule is a trader giving a VAT number is obliged to charge VAT at the rate applicable at the time even if the receipt/tax invoice does not individualise the goods from the VAT element.
However the exception to this advice is where you purchase a zero-rated item for VAT purposes from a trader who is VAT registered, when obviously, that trader, although registered for VAT is under no obligation to add VAT to the sale price, thus preventing you from reclaiming VAT on such a purchase as no VAT was charged to you in the first place.