Lungworm is rare in Scotland, most cases have been in dogs that have travelled over the border and spent time in England.
Bayer's website has a map of lungworm cases to give you an idea of risk areas.
If anyone is concerned about lungworm, particularly those in risk areas, and particularly if their dog eats slugs and snails, or grass where these are common, there are several treatments licensed to prevent lungworm when dosed monthly.
Advocate (or other brands are available) not only treats and prevents lungworm but also treats and prevents fleas, for which we should all treat monthly to prevent. The active ingredient that deals with lungworm is moxidectin so you can find the alternative. However, this is not an excuse to use things like cattle wormers that include this ingredient as the formulations for dogs have been tested rigorously to ensure safety as many dogs (particularly collies) can be sensitive to this class of drugs, so please always use as directed on the label ie. dog medication only for dogs.
There are also milbemycin tablets including Milbemax that treat worms in general including lungworm.
Hope that sheds some light on it for you.