Yea I knew it'd be high, Scotland's not really know for its lovely sunny beaches and perfect weather is it.
I've put a link to some ballistics using a 165gr berger bullets with both a 300winmag and 308, in a 30mph wind with nothing changing except for the velocity.
You can see that even though there is a big difference in muzzle velocity and 300yards the wind drift is 4" difference which is a bit but is nothing in comparison the 17" of the 300 win mag.
Sure you can probably get a better wind bucking load but 30-40 mph wind is very strong wind and unless you are very good at reading wind or have something like a 50bmg, it will not be an easy shot.
And with the 300 win mag, to miss judge the wind as 30mph when its actually 40mph, your shot will be off by 6 inches.