This is actually an interesting additional complication. If a units permanent base is in Scotland, but they are posted overseas, do they still pay the higher Scottish rate of tax, because that is their permanent UK residence, or do they drop to the rest of the UK's tax system?
To me, this looks like it has the potential for becoming as much a nightmare as the US tax system which I have the misfortune of having to deal with.
I was always paid the same basic wage and taxed the same as per my rank at the time wherever I was posted, you would see an adjustment as a separate entry for exchange variables as LP describes, but, when on active tours (NI, UN, ME etc) there would also be another entry as we got extra for certain tours and active duty.
I think the pads got more than the single barrack boys when away on tours, which was the only gripe.
Nothing changed when posted temporarily (6-24mth tours) to somewhere away from your main barracks or unit which would/could be home for around 3yrs on average anywhere in the world, unless you were a home guard regiment with a constant UK residence and only doing short tours.
Either way, I saw no difference in my pay as far as tax was concerned, as long as there was enough in the account for a constant flow of beers and dirty women, I doubt if many of us took that much notice.