
I found it much cheaper to get Busters Metacam from an on-line company and just pay the vet for a prescription. The 'script cost about �12 (icluding VAT), but this covered 3 repeats (so 4 x 180ml bottles in total). The cost of the Metecam on-line is �18.18 (including VAT) + �2.50 postage, compared to my vets price of over �60.
Massive saving, especially as Buster was taking a dosage to 70kg mark, so the bottles didn't last long.
I used petdrugsonline, I found them the cheapest for Metecam and never had a problem with them.
As the Metecam lasts you a while, your vet may only do 1 or 2 repeats on it (I think the dog needs a vet check every 12 months on Metecam, before a 'script can be given out), but the cost of the 'scrip then effectively becomes cheaper per bottle (if that makes sense)
Sorry if this has not answered your question, but I was not sure what you meant about just asking about VAT.
ETA, sorry, only just noticed your update! My vet was amazed at the price I was paying for Metecam, he says it's much less than the his surgery can get it for!