Thanks for all the pointers, all. Route I've ended up going for my commute up here for the next few weeks is thus:
http://goo.gl/maps/8meG3
And it is delightful! Tatton Park with all the deer and stuff particularly nice. To think I was going to take dual carriageways all the way ...
Cycling here really is a different experience from other places I've ridden regularly, particularly when it comes to other riders and driver behaviour.
South Manchester / Cheshire wise is a different thing again - lots, lots more utility and leisure cyclists, and loads of mountain bikers and roadies - seems everyone round here has a passing interest in cycling. And driver behaviour has been exemplary - I think I've had one pass that made me slightly uncomfortable but would be considered fairly normal anywhere else, but I've had tons of patient waiting and almost unnecessary considerateness. And the countryside is lovely. Bloody great place to be a cyclist.