Hi Gareth,
Here's hoping that there's someone on the forum that is from, or knows your neck of the woods and can help you out.
Otherwise you could scout out the locations of interest you've found on topographic maps to see of there's any sweet parking spots. It's a lot easier nowadays too with the likes of Google Earth, online maps etc. to the point of checking locations out without moving a muscle.
Height will definitely help you with 'local' copies and it's a lot easier to drive up a big hill taking your antenna with you than trying to raise it to a similar height from your home QTH. (Can you imagine how many scaffold poles you'd need!
)
Don't forget we're coming up to the summer 'skip' or Sporadic E season where greater distances of transmissions and reception can be had, (DX). It doesn't have to be all Sideband radio stuff either and I had some great contacts into Germany and Austria a couple of summers ago on mid-block or Euro frequencies on FM. (Yes, FM!)
In which case you might find a better location by going lower to sea level. (What's he on about?!?!) You're not far from the North Sea coastline which surprisingly to some can help with radio transmissions and as you can imagine there's nothing but sea between you and continental Europe from up there. If on air activity is up you could get some great DX on a summers afternoon and right through to the 'greyline' activity as the sun sets. (This can be done at dawn too but not many fancy getting up that early.
)
Anyway, food for thought.
I wish you all the best with it.
73,
Victor