When next registering so you can vote, remember to choose the option which blocks your info from being sold on to marketing firms. This should cut down at least some of the scammers.
Also register with the Mail & Telephone Preference Services, and then you know that if ANYONE contacts you out of the blue, they are going to be either abroad and exempt from the usual rules or UK-based, dishonest money-grabbers. No decent firm will contact you if the MPS and TPS are registered on your details.