If you buy a DH bike, sure you will love it in the Alps - for your one or two week holiday.
Then back in the UK you will stuck riding only at Aston / Cwn Carn, a pale immatation of the Alps.
I built up a bike that would do it all - Transition Covert, uppy downy, big forks, big brakes, big bars etc etc. Rides XC fine, rode the Alps fine. In fact I didnt need more in the Alps, more would have been beyond my skill level. Back home Im still competitive at the Bristol Bike Fest, fine doing SITS and fine riding it everywhere.
So just sort out your bike with better suspension and brakes. Unless you really want to give up XC and just race DH in the UK all the time. One of my mates does that, the rest who dabbled at DH ended up selling them because the couldnt justify a bike that got used so little.