hi dan,
sounds like your in the same boat as me! I started planning the Jogle with 3 friends, and one by one they all dropped out! So basically im doing the same as you and doing it solo having never done anything like it before and only started cycling properly about 6 weeks ago! im starting from john o groats on the 24th though and aiming to take 9 days, I travel up on the 23rd, stay at the seaview that night then hoping to be up and started by 7 on the 24th.
I was also debating whether to buy a sat nav but no way im spending hundreds of pounds on way, I bought a small map the other day and im going to mark the route on there and that'll do, far cheaper but no doubt I will get lost at some point!