London to the Shetlands
I did it in a C172N a few years ago - see my article in Pilot magazine's Oct 2006 issue 'Beating the Bounds'.
I flew from Stapleford to Carlisle more or less in a straight line, then across to Campletown, up the west coast and Great Glen to Inverness to avoid bad weather on the east coast. On day 2, I flew up to the northern tip of the Shetlands and back to Sumburgh for fuel. Then it was back to Dundee via Wick and overhead Aberdeen.
With hindsight, I would have spend more time flying around the islands but I was worried about being weathered in for days. On a previous trip to the Orkneys, I met some pilots who had to leave their microlights up there and come back for them weeks later when the weather improved.