Sorry gentlemen, I must correct you: all the routes were created on Basecamp.
We do use a GoogleMap based system for small routes that feature in the regular issues, but all the routing for the touring supplements is entirely constructed in Basecamp.
Why is it giving Geezer ludicrous mileages? I have no idea. I have it open on screen at the moment. Day One: 279 miles, 8hrs 17mins.
My immediate suspicion is that you'll - quite understandably - have put Basecamp into bike mode. This is an innocent but fatal mistake: the software makes irrational decisions in bike mode. Put it into generic "driving" mode (car icon on the route panel) and it behaves in a predictable, manageable way and allows a bit of motorway to be included in a route where it's needed; in bike mode, it will get off the motorway at every junction, even if you want some time-saving motorway to eat a few miles.
Also check the route is accurately rendered on the roads without any sections doubling back. This can be caused by disagreements between the map generations: those routes were plotted in 2013. If you're on this year's map, it's possible that it's mis-interpreting some of the point locations and putting them on the wrong sides of dual carriageways (though I'm on the latest map and it's fine). You should be able to see doubled sections, which will show up as darker/thicker bits: zoom in on them and use the black-arrow tool to move any errant waypoints to the correct side of whatever motorway/dual carriageway is causing the problems.
All the routes are constructed with fixed points dividing each day's ride into legs, with shaping points between them. The fixed waypoints are generally cafes, though on some routes they may be points of interest (the first day of the France tour you're looking at, for instance, has a lot of the D-Day beach locations marked as fixed waypoints). But generally, I put in three median waypoints to divide each day's ride into four chunks: start to coffee, coffee to lunch, lunch to afternoon coffee, afternoon coffee to hotel. The waypoints will appear in your "favourites" menu so, if you go astray, you can select one directly from there and ride to it to pick the route back up. Likewise, if you think you need to skip a section, you can select one and ride to it on the fastest-route method - may cut out some of the good roads, but get you back on schedule.
Even when checking the routes - and doing the recalculating stage, as Richard recommends (essential for any downloaded route because of the map-generation issue) – the Navigator will recalculate each route again once you send it to the unit. So if you're having trouble with the relatively point-light routes (day six has six points for a 200-mile day) you may want to edit it before the device-transfer stage, increasing the number of points to keep the route on track. Adding shaping points (drag with the black arrow to force a shaping point) reduces the scope for it to misunderstand where it's supposed to go - and it's when it decides to go off on a different road that you get more miles and also miss the roads you're doing the trip to enjoy. You can add more fixed waypoints if you like but (a) if you ride past a fixed waypoint for whatever reason, then the nav will want to turn round and go back to it (hence we don't use too many of those) and (b) there's a limit of 25 waypoints on a route, but no practical limit to the number of shaping points you can add. The best place to add a shaping point, generally, is just AFTER a junction or turn - as that will ensure the device links junction to junction, keeping you on the roads.
As a final note, I would strongly advise against using the twisty-road setting when following a preplanned route. There is no way of predicting where it will go, but the chances of it following the planned route – which is created with Basecamp basing its decision on the default "fastest" setting - will reduce dramatically the fewer waypoints are used. If there's a stretch of 40 miles between points, the sat nav can decide to go anywhere in that space when it's on the twisty setting. And the nature of this long tour is that on some days there are stretches that are decidedly untwisty - because all touring is a compromise between riding twisty roads (raising mileage, taking time) and getting to the destination without being in the saddle for 14 hours...
If you continue to have problems, email us at the office.