Hi Ruard
I am not familar with what flies are recommended for Orkney, and my experience in fishing loughs/lochs for wild browns is limited enough.
I would happily fish traditional lough style any wild trout/sea trout loch/lough with the following
Golden Olive Bumble
Claret Bumble
Clan Chief
KingsMill
Green Peter
Claret Dabbler
Silver Dabbler
Olive Dabbler
Claret Sedgehog / Halfhog
Muddler
Invicta
Silver Invicta
Dunkeld
Thunder And Lightning - trout version
A good start would be Stan Headleys Book -
http://www.amazon.co.uk/Trout-Salmon-Fl ... 1873674260
I think he is from orkney.
Surely there is an honest scotsman here that can point you in the right direction

for LOUGH flies for orkney.