DFC. The following are not in the same order as your charges.
1. I don't work for NATS.
2. You can fly at the base of controlled airspace VFR without a clearance, thus 5,500ft. until you reach Class E airspace (or at least it was Class E around Cumbernauld below 6,000 ft when I was there - not sure of airspace changes since). You don't need a clearence to enter Class E if VFR.
3. Minimum safe enroute altitudes are for aircraft flying on instruments. You wouldn't be flying VFR in IMC now, would you? The minimum VFR altitude is 500 ft from any person, vessel, vehicle or structure because if flying VFR in the UK, you should be able to see any terrain in the way.
4. Of course you should go VFR into Cumbernauld. Easy-peasy to go through Class E at 2,000 ft without bothering anyone and by all means call EGPH App for a Flight Information Service so they can identify you. If you can't get into Caumbernauld VFR, then go IFR and get an approach to cloud break from Edinburgh.
5. My point was that at FL85 you're probably navigating on instruments and that such an altitude is about as inconvenient as can be for Scottish Control and Edinburgh Radar.
Counter-rant over.