He's based in Daventry. As has been said, if you were going down the denali route I'd purchase his modified adventure mount solution (though I still prefer the bmw oems and their position on the GS - for me, seem to work better with the GS). As for the install, it's going to be straightforward - just some patience required. If you want to remove lots of bodywork for a 'clean installation', have a look at Nick Hodge's channel on YT. But otherwise, if the install is around 200 that sounds like a fair price.