I appreciate the response and link. The John O'Groats to Land's End route is exactly what I have in mind with a detour to the town in the north of Scotland from which my mother's maternal grandparents emigrated. I think I may still have some cousins there.
You need to be aware that there is no definitive John o'Groats to Lands End route. There are publications that each describe a route specific to that publication. There are plenty of people on the CTC forums mentioned elsewhere on this thread and you need to be aware that the opinions of some of the posters need to be treated cautiously as they hold strong opinions about their own route preferences.
I live in the UK and have cycled Lands End to John o'Groats and John o'Groats to Lands End. I used a Philips UK road Atlas which was cheap, showed the approximate location of camp sites and was disposable once I tore out the relevant pages to use on the rides. The biggest obstacle is getting to/from John o'Groats. There is a rail link but the trains have limited capacity for bikes and pre-booking is essential. The train guards will not let you board the train without the relevant piece of paper showing that you have a cycle reservation.
Be prepared to be underwhelmed by John o'Groats and Lands End. There are better places to start and end cycle rides. The big bit in the middle is worth joining the two places together by bike though. As someone else mentioned, there's tiny flies called midges which can make your life hell. They tend to disappear when it's raining or windy which means that you'll be unmolested in Scotland