Apparently wood worms of various species are a worldwide problem, but I think here in the U.S., the common termite is more of a problem, especially in those areas that do not experience a 'hard freeze' winter. As the one article mentioned, the woodworm seems more prevalent on the East coast of America.
I did a quick search for my own edification, using ' U.S. woodworm infestation ' on Google. Here's one result -
http://en.wikipedia.org/wiki/Woodworm , and another, -
http://blog.ecosmart.com/index.php/2009/12/01/woodworm-treatment/
I would not want to be plagued with the little devils as you are; it sounds like they are a '******' (pun) to deal with. The use of an electric bug zapper(s) might be needed in the Spring when the females are flitting about looking for a ground-bound male to mate with. Insecticide poison applied with a brush
might be sufficient, but I'm inclined to wage a war that might be considered 'mutually assured destruction' by using sprays of various sorts; of course,
I would be the only combatant wearing a suitable gas mask! LOL I would probably opt for the good old weapon of choice, the 'garden sprayer', to squirt/spray a properly diluted concentrated insecticide into every nook and cranny that a brush won't reach, along with every surface that the brush did cover.
Repeated applications in the Spring might be called for in case some of the critters arrive 'late for the party' and didn't get a taste of the 'kool-aid' in the first application's punchbowl.
I don't know if a product like this is available to you in the U.K., but there are poisons available here that you mix
into the paint before applying, and is supposed to be effective against spiders and such; it would be good to find that the stuff is lethal to woodworms as they try to make their 'Great Escape'. Considering the vast amount of wood (apart from the block walls) that you have there that needs treatment, I would see if I could buy the poison in bulk (like 50 gal. drums of it), dig in for the long battle, do a lot of reconnoitering with a good, strong beam flashlight for evidence of boreholes, and lay out an intensive, thorough battle-plan. The 'Armageddon Approach' over here in the U.S. would be to hire a specialist company whose plan of attack is to littorally bag the entire structure in an air tight tent, and then pump in a toxic atmosphere to bugs and leave the apparatus there under a positive pressure for days (weeks ?); this being done while the human occupants are residing elsewhere!
Extreme measures are sometimes called for against the insect world; remember that THEY outnumber us 'billions to one', so we have to fight dirty to not only win the battle, but also the war! Good Luck, and be merciless!
Also later I found that the cars left in there were covered in a fine sawdust, which is created when the larvae are eating themselves new holes in the wood. I have read that they only like bare wood, so painting it alone should be enough to ensure that they are unlikely to lay their eggs on that wood in the future, although that doesn't do anything to kill the larvae that are already in the wood and will eventually eat their way out.
If you did open it fully you could be sure it wouldn't unroll unexpectedly but the opening is very high and you would then need a step to reach up and grab it and pull it down again.
