I think you'll be dead and hate your bike by the time May rolls around!
Okay, I don't know what kind of shape you're in now, or what you've been doing over the last year, so I'm making some assumptions... that looks like a pretty tough training schedule to me. My understanding is that spinning classes are pretty intense... classify them as work-out days. 30-40 miles is enough time/distance that it also qualifies as work-out, unless you're riding d@mn easy. Does this schedule include enough recovery time? Remember... recovery is when you get stronger.
250 miles a week is a lot, even if you've been training regularly for several years, and you should plan on at least a 1 week taper prior to the Brevet, if you want to do your best. Again, the mileage and effort is wasted if you don't allow adequate recovery.
Finally, it's kind of the reverse of the usual training schedule... sort of a base2/build schedule now, base later.
What do I think? It looks like weather and daylight hours, rather than your goal, drive your training plan. (Granted, we all do that to some extent.) Just don't overlook the value of the really easy, totally aerobic miles, especially since you're targetting distance events. And you need to do them now, so they can serve as a foundation for the harder, longer work you'll roll in later. I think your plan can work, but you might consider fewer spinning classes for now, to make room for more base work.
Good luck with it!