My old commute sounds similar, unlit A roads, unlit B roads and country lanes, including single track.
Only rear light I will now use is the cateye TL-LD1100
http://www.cateye.com/en/products/detail/TL-LD1100/
various options including 1 level or 2 levels flashing/static or any combination inbetween, usually only need 1 level flashing to get seen - very rarely need both levels on (and I beleive in being seen). One of the things I really like about this light, is that the lights have a focal point where it is bright, but as you get closer and pass to the side, it is nowhere near as bright and certain not blinding unlike some.
It is one of the few is visible from 270 degrees. First bought more than 8 years ago, still going strong and there is an optional adaptor to fit to a pannier rack if single screw is not an option as well as standard seat post and belt/rucksack clip.
We run these with rechargable AA batteries and usually go several weeks without needing to recharge them. (On tour we had them on each and every day in the UK on flashing, and a set of batteries would last a week used all day every day on single strip flashing mode.) All 4 bikes have one (we have the screwed on, rather than unclippable).