We are on a hill directly facing onto the Cairngorms and I would recommend starting with things that will be likely to do well, so that the more risky things can be added later when it is less traumatic if they fail as you will still have some successes!
Greengage sounds like a good one. We haven't tries that but we have planted damson Merryweather and that has been a great success, it's only been in a year and is still a small thing but had lots of fruit on it this year so would def recommend that, experts say damsons are very good for exposed and cold places.
Also consider quince, they are tougher than some of the apples (and will pollinate any apple so very useful if you then get normal apple trees where some need several pollinators, plus the blossom is amazing)