Furkids UK       

D.A.P.: available as plug-in diffuser, spray or collar. Seems to relax anxious and stressed dogs. Works well with my bunch. Available in pharmacies or Internet shops.

Bach Flower Rescue Remedy: calming effect in stressful situations such as visits to the vet, being left alone, adapting to new surrounding.  Fear of loud noises, such as firework and thunder. Available in pharmacies or Internet shops in form of essence or globuli. Works wonders with my over-anxious Aussie. 

Some dog owners I know made good experience with the Stormdefender. Although originally created for thunder-phobic dogs (surprise, surprise), it seems to help with fireqwors as well.