Western Isles
I think niknak has made a very good point, as traffic levels have increased dual validations become more difficult to maintain, for the controller and probably for the rostering of either unit that the controller is working at!
FISO is used for Ambulance and Emergency callouts within HIAL.
In the past I can remember controllers being used at Airfields such as Tiree and Islay(Dual validations in some cases or ATCO/manager). As niknak rightly says they have been replaced at quieter units over the years. If SCRATCOH is to be applied correctly, imagine how many controllers would be needed to run these units if FISO did not provide the on-call requirement? How many controllers would be willing to work at the FISO only units when there is limited traffic?
Don't think Parkfell can be a Senior Manager niknak as if some posts are correct are there any left?