It could be worth phoning round the pharmacy departments of the big stores (Tesco, Asda, etc) to see what they can offer.
The number of tablets you require is equal to the number of days that you'll be in a malaria zone + 9 . (You need to take one a day from 2 days prior to entering the zone to the 7th day after leaving it). A site such as
http://www.chemist2go.co.uk/product.asp?id=5191
charge �2.25 per tablet, so protection for a 14 day holiday will cost you 23 x �2.25 = �51.25.
Further information on Malarone is here:
http://www.studenthealth.co.uk/leaflets/Malarone.htm
Hoping this helps,
Chris