@philinmerthyr - I don't really think I have much experience, but knowing your rides from the other thread I would say you already have a decent enough level of fitness, and any distance work you can put in would only stand you in good stead.
If you use gels and electrolyte tablets, use the guide
@Reece posted about, as its got a good amount of info for pre ride, the ride and post riding which seems relevant to the distance work we are doing.
http://highfive.co.uk/high5-faster-and-further/road-cycling-nutrition-guides/sportive
Well done on the weight loss, but dont worry too much about that, so long as your core fitness is good (which it seems to be judging by your strava rides) cover your bases with 70-80% of the distance, like your planning, and the elevation, which you've already nailed. Somebody said to me once if your doing a long endurance event, always make sure you can comfortably do 75% of it, and the rest will follow naturally on the day.
But yeah, I think your plan is good. I plan to do 1xMC, 1x80 miler, a few 20milers with hills and quite a few 20 mile trips into town , the flat way, with rest days of course. The last week I'm just going to do short spinning trips.
Take from the above what you want, but I know your a regular climber living where you live, so the base is all good. What time is your start?