Thanks for all the positive comments
The routesheet and information has been uploaded to AUK after a route check last weekend. There should be some sort of award for the most breakfasts consumed on a 600, as I've researched lots of extra cafes/Wetherspoons, especially for Sunday morning! It might be a shoestring event, but it could get expensive!
There IS an AWFUL lot of flat, as you'd expect, but please forgive the odd proper hill, especially Foxby Hill from Gainsborough, Canwick Hill out of Lincoln and some rolling lumps in N Herts & Essex. It will be a little more than 2km over distance, due to avoiding the A15/16/17 etc, but hey, the general lack of hills must be in my favour! There are some cobbled streets to wake you up in Lincoln city centre, which should be fun too!