Bike shopping!

So further to my last thread, the Wee Ride seat isn't working for me and ds either as it's aggravating my lingering SPD. Sooooo.... lovely dh has offered to get me a new, shiny bike as a combined birthday, anniversary and Christmas present!

Budget is up to £300. I'm looking for a ladies frame, good and sturdy to carry a rear bike seat, that will deal with country lanes and the odd little hill (I need some gears!). Maximum round trip we'd be doing is 15 or so miles, mostly it's for v local pootling abou, and not at any great speed. Needs mudguards and all that jazz.

I'm 5'9" so it needs to come in a 19" or so frame size, I think?

Going to head to the local bike shop in the week, but can anyone recommend me anything to look out for - or avoid?