I've flown from Birmingham to Orkney twice (Robin and 172).
Recommend Easterly route. Watch out for the gap between Manchester and Leeds controlled airspace, its not very big!
If its not too busy at MCR they may let you through the zone.
Large Danger area SW of Newcastle, dont remember the name of it.
Route up to SAB VOR over the water and east of Leuchars, this can be quite active
Both times I stopped in Aberdeen for fuel.
Coasted out at Banff (northbound). Coasted in at Wick (southbound)
Doable in a day quite hard work.
But definitely go for it
First time was 1993 IMC, second time last summer (IMC now lapsed)
No other specific advice to offer