Yes, you need to verify every day for the last 5 years. You can use a personal reference to verify periods when you weren't working, or in education. If I remember correctly, for personal references, you have to use a different one for each gap.
You will at some point need to apply for a basic disclosure from Disclosure Scotland, but it only lasts so long, so I would wait until you are told to. The rest regarding the pass should be done by your company / BAA.