I tried to import Provent-a-Mite from the States about 6 weeks ago and have heard nothing so assumed it either didn't get sent or got seized at Customs.
This is the stupid legislation that comes from the EC. It's also why gardening products that have been used for years are now also banned. While there some chemical pesticides that should have been banned years ago for damaging the environment and people, I think a lot of it is just bureacracy gone mad.
I haven't come up with an alternative in the UK either but phoned our Reptile Vet and they recommend Frontline - yes the same one you use for cats and dogs. What they told me to do was take the snake out of the viv, spray the Frontline on rubber gloves and let the snake slither through then clean the viv and spray that and the viv furniture but don't put the snake back in until all the fumes had dissipated. DO NOT SPRAY DIRECTLY ON THE SNAKE AND AVOID THE HEAD AREA.
You then repeat the process exactly 2 weeks later.
I did this and haven't seen a mite since (we had a rescue Royal that had mites).
I'd check with your vet first though. There is an injection your snake can get but I can't remember the name of it.