I had given this a lot of thought earlier in the week but came up with nothing. Then I saw that it was suggested it could be a Skipper type of Butterfly, but like you I think the antennae are wrong.
I have found a moth which isn't exactly right but is found at altitude over 600m in Scotland a Broad-bordered White Underwing - Anarta melanopa, one of the Noctuidae » Hadeninae (I was searching for my own unidentified Noctuid when I saw it)
UKMoths - Broad-bordered White Underwing Anarta melanopa
I think you could see what other Hadeninae are in your area and go from there.