The Hay Experts - the perfect place to purchase all sorts of lovely different varieties of hay and natural treats for your guineas (and rabbits!). They also sell disinfectants, dried food including Oxbow and Science Selective, along with Oxbow Critical Care.
Dog Health - Four Seasons Anti-Parasitic wormer is available from this site. It is a natural wormer that is suitable for guineas.
Microfibre Towels on eBay - these towels are super absorbent and great for drying guineas after their pampering session:)