Hi Lee,
with my experience of my 508GT, with keyless, I can tell you it's perfect now. Yes you're right in that Peugeot has had a lot of problems with the system, mainly the sensors in the handles. I had the driver one replaced a couple of years ago and ever since it's been perfect.
There are many things that can interfere with it's correct operation. Main ones other than the handle playing up are extreme cold, extreme heat water and dirt on handle and also cold hands. (that'll be the problem for the missus that on)
I would think with you're car being so new it'll be a dodgy handle (sorry). I doubt it would be the car going into economy. I parked my car at Heathrow for 5 weeks last winter and my handles worked fine when I came back to it.
Grumpy.