The site lungworm.co.uk is owned and made by Bayer. Who manufacture.... Advocate. So when they suggest you go to your vet and ask about a 'spot-on' for it - manufacturing as they do, the only one - they are recommending their own product. This wouldn't be so bad if they didn't try to have the site masquerade as a factual site, unaffiliated to any company - unless you read the small print.
There are 2 alternatives to Advocate. One is Milbemax, which is also a round and tape wormer and a prescription med as well. Or there is Panacur - also a round and tape wormer, but non-prescription. Both are oral meds, no spot-ons. Panacur is a bit of a pain because you have to give it over many days, but you just add it to the food.
Study showing that Panacur (fenbendazole) is at least as effective as Advocate (imidaclorid or whatever spot-on):
http://www.ncbi.nlm.nih.gov/pubmed/17544583If you live in the US there was also until recently Interceptor - which is an oral monthly heartworm preventative, but works on lungworm as well - since it is the active ingredient against lungworm which is in Milbemax (milbemycine oxime).