I’ve done PPdS a couple of times and going again this year. I have a 5yr old Giant Reign with 160 forks/RP23 and it’s a good all round Alps bike. Our PPdS/Alps group have a variety of kit most forks are 140 or 160.
IMO it depends totally on the type of trails and how aggressively you ride it (as others have said) as to what setup you’ll want.
You should take some time there to tune your shocks to the conditions and the riding sytle.
If you will not use the 160s when you get back the purchase is questionable (you could resell them on here ?)
How are your brakes, do you have any body armour/pads, suitable tyres (eg Maxxis Highrollers) ? Upgrades here may be better use of your £’s
You can also rent a full DH bike for a day for a play about once you are into the riding. In all liklehood after 2 weeks of Alps riding you’ll probably need to spend some money on maintenance so best to leave something in the kitty.