I recently spoke to my vet when the girls had KC. When I asked him about prevention he told me that the only licenced product is Advocate. Panacur is used as a wormer if lungworm is present but apparently its required in high doses so isn't used as a preventative measure. He also said that there was no definitive test for lungworm although a fecal sample may show them present, and they can also do blood tests, but again they may not show up. The slugs and snails have to be ingested. Milbemax covers heartworm, not present in UK, which I think is confused with lungworm which lives in the heart 
I found this website which talks about Advocate but confusingly gives a link to milbemax. http://www.barrieranimalcareclinic.co.uk/lungworm.htm
I'm really not keen on Advocate and I don't routinely treat for fleas, only when they get them. They are both wormed with Milbemax 1/4ly. I have some Advocate as Ebony had a baby slug caught in her feathers and I can't be sure that she didn't try to bite it off. Advocate as I understand it doesn't cover worms such as Tape worms, so a wormer for them is needed.
The whole thing seems to be confusing to say the least. I just don't want to overdose them on all the chemicals, ie Advocate, Milbemax and frontline, just to prevent. Also in time does it mean that the worms, fleas, ticks etc will become immune? I suppose you just have to do a risk assessment for lungworm and whether or not your dog eats slugs/snails or other dogs poo.
We're down in Dorset & Purdey was diagnosed with Lungworm a few years ago. She'd had it for approximately 8 months (dismissed by vets twice due to her symptoms not being typical of the condition) - we nearly lost her to double pneumonia before they found the cause. There are 3 ways for a vet to check for lungworm infestation - 1. treat & see if dog improves 2. stool sample testing & 3. Lungwashes (the test that does give a definitive result
) which Purdey had & showed up 2 different strains of the worms
She was treated with 1 month of Panacur (at quite a high dose) with 1 week break then a further week to kill any unhatched larvae not killed the 1st time round.
The reason it also 'known' or sometimes called heartworm is because of the damage it does to the heart - with the lungs massively enlarged & infested, this puts pressure on the heart, which in Purdeys case has left some damage to the right side & in turn causes slightly higher blood pressure in the heart.
Also, I must add that the dogs don't have to ingest the slugs/snails to contract the illness - there slippery trail does the damage too. Anywhere the slug has been could be infected, including rainwater puddles, toys/dishes left in the garden & also infected dogs & foxes feces. Our vets recently had a case referred of a dog that was having seizures - a MRI scan showed the lungworm had migrated to it's brain
(unheard by our vet before)
The treatment itself can be as dangerous as the condition in some cases - for severe infestations there is a possibility of the dog dying within 48 of being treated.
I now use Advocate but not every month - more when I think they need it. Ticks really don't worry me & I use the O-Tom if we come across one but TBH, fleas & ticks don't seem to be a problem for my girls.
There is a national study being done on Lungworm, so hopefully in the not too distant future, we will all have the
same information as to how best to prevent/cure this condition.
A few months back, Tinker slowly became 'not her usual self' - vets diagnose possible pneumonia or lungworm - she was treated for both & is much better. In Tinkers case, rather than more invasive tests - dual treatment seemed to do the trick but unfortunately we'll never know what it actually was
Our vets also insist on all dogs going in for surgery, to be treated with Advocate just in case the dog were to have undiagnosed Lungworm - blood not clotting is another symptom but sometimes too late when on the operating table.
hope that helps a little
Lindsey x
