Shooters suck at advertising sadly. Information on many events is word of mouth and even then barely existent!
You've missed most of the Nationals for this year, as they tend to be spring/winter, because bodies like the NSRA are busy running the outdoor cartridge rifle meetings in the summer, whereas in the winter they just have the postals comps to administer, so slot in the indoor meetings (which are not weather sensitive) during that period. Also, as Commonwealth and Olympic Games tend to be in the Northern Hemisphere summer (although as it happens 2018 CWG and 2016 OG are both Southern Hemisphere), it makes sense not to be around June-August because otherwise in Games Years your top athletes are busy doing other more important things than travelling to clashing domestic meetings.
Unfortunately as you're in Scotlandshire, most of the meetings also involve a fair amount of travelling.
The Scottish ones were March/April depending on whether you want Rifle or Pistol.
Scottish Smallbore Rifle Association
Scottish Pistol Association
If you're wondering, I listed the SSRA, as the Scottish Air Rifle and Pistol Association are more FT/HFT/Benchrest focussed than ISSF-10m, which the SSRA specialises in. That said, SARPA do seem to run a series of 10m Air Pistol events through the summer, so could be worth checking them out if you're pistoleering rather than rifle shooting.
A brief list (there are lots more, Google is your friend, if not Scotland then certainly a few more up in North England/Borders region that I don't know about):
January
British Pistol Club January Open (Bisley)
Geoff Partridge Memorial Shoot (Aldersley, Wolverhampton),
February
British Open Airgun Meeting (Bisley).
March
Scottish Air Rifle Open
Swadlincote 10M Open (Derbyshire)
April
Scottish Air Pistol Open
May
ESSU Open (Bisley)
June
British Pistol Club Open Championships (Bisley?)
October
Welsh Air Open (Cardiff)
There's also a North Wales Airgun meeting in the Autumn I think, but that's not happening this year for various reasons, but it will be back next year. Oddly enough that's actually held in Shropshire I think, being the best large indoor space the organisers could lay their hands on for a reasonable price,.