So ladies and gentlemen...
I did some googling and it seemed very wise to pre-book accommodation as there really wasn't much (they want you to stay more than 1 day, mostly).
So I have done my best to split up the route into decent sized chunks, having read all your comments above about slow sections. I hope I've got this right.
I'd be very grateful for any comments on the below items. I have accommodation booked at all the destinations but it's all cancellable if I have made a major mistake.
18 June, 205km, Newcastle to Edinburgh
19 June, 255km, Edinburgh to Inverness
20 June, 182km, Inverness to Wick
21 June, 85km, Wick to Melvich
22 June, 120km, Melvich to Kinlochbervie
23 June, 80km, Kinlochbervie to Lochinver
24 June, 150km, Lochinver to Gairloch. (this day was really hard to find accommodation for)
25 June, 120km, Gairloch to Balmacara
26 June, 116km, Balmacara to Fort William
27 June, 110km, Fort William to Oban via Mull
From Oban we will make our way back to Newcastle but I think we can be more relaxed about accommodation as I expect we will find something, so I may not bother pre-planning.
By the way, I said to my chap "it's cool to be at Fort William as we can see Ben Nevis" and he said "What is Ben Nevis?"
Any suggestions of improvements/better routes please let me know!