I'm no expert, but a couple of things come to mind that you could try:
There is a specialist lawyer that has a column in RIDE magazine, his firm specialises in bike claims but the principals hold true,so it could be worth a phone call to his firm for advice. Often he seems to say that the insurers always take the easiest way out which is to pass the buck back to the individual, which is not right.
You could employ a solicitor to act on your behalf, his costs then become part of your claim.
There are companies that offer to act on your behalf to manage your claim, again their costs would be recoverable. pick up a leaflet from any body repair shop.
Of course what is covered is always buried in the small print.
And unless specifically included trailers have always been a bit of a grey area, as they are with breakdown cover.
Hope this may be some help, but you do seem to be stuck between the 'big boys' none of whom want to shell out!
