I can't see why they(the dealer) can't stick another hose on there to try if it's the hose that is causing it. It may not last for too long if using a sub-par hose, but at least you'd be able to go for longer drives until MMC get it together on their end. It's a hose, not, say, a pump, camshaft or something.
They probably could do that as a temporary measure - if I could find the time to round there over the next few weeks (100 mile round trip !).
