(I am fully committed to become an ATCO and I am planning to write to most airports in Scotland and England and visit them)
The majority of Scottish airports are operated by HIAL. HIAL have in the recent past selected ATCOs from the ATSA/ATSOA, Fire service and Admin grades. (albeit in small numbers) Members of these grades often do FIS as a supplementary job to their main paid job. Allowances are paid for being a FISO and carrying out MET observing. - This might be another route towards your final goal.
An expensive trip to visit all or most of these locations, however I think you would be made most welcome.
-However you get there best wishes.
