screwfix do a glass fibre kit that says it can be used for filling large gaps, they also do a couple of different types of filler. looks a pretty useful thing to know of. notbad price either.
used it before on batt box and still holding up strong after alot od mud and water
Got my snorkel from mantec direct. Great way to buy them. Dont know about postage as I picked it up from their office. Still pleased with it 18 months later
had this prob today
managed to get a 13mm socket on with the aid of a hammer then used a breaker bar to remove, also give a good blast of WD40 and leave a few mins did the trick