Here it is:

VioVet.co.uk - Pet Medication & Food - Frontline, Drontal, Hills, Royal Canin, James Wellbeloved, Feliway, DAP. - VioVet

Just wanted to add that at just over £16 for one diffuser there may well be cheaper places out there but for 2 of them plus the spray it was the best 'package' price I found.