Eeyore wrote: My wife is in her 60s and needs a new bike after an unsuccessful flirtation with a Danish sit-up-and-beg. I would very much appreciate advice on what bikes she should consider. She is uneasy about being unable to put a foot down when stopping, so a low bottom bracket seems desirable, as does a step-through frame. Rear pannier braze-ons are needed and fronts would be helpful but not essential.....
There are 'utility bikes' with very low step through frame designs that might suit. Was there anything in particular that caused a problem with the sit-up and beg bike?
Essentially the choice for everyday utility cycling divides neatly between 'lightweight and impractical' and 'heavier but more practical'. The mythic 'lightweight and practical' bike has yet to be made at all, leave alone at a price. Fortunately it turns out that the weight of the bike is not so important; it takes a very heavy bike to slow you by more than 10% and if you ride five miles or so that adds a mere couple of minutes to your journey. More gears allows hills, shopping loads and headwinds to be dealt with, so a singlespeed bike won't suit so well as one with gears.
So anyway, some bikes worth considering would be models from Gazelle, Batavus, Koga Miyata; these would typically be lighter in weight than (say) a hoprider (which is a very good spec for the price) but far better made, usually designed to last decades. They also variously try to tread the line between weight and practicality. Unfortunately they are also somewhat more expensive, so you would be looking at a used machine rather than a new one at that price.
But in simple terms you could have a roadster with an IGH (say a Nexus 7) and a chaincase, and at the other end of the spectrum there are things that look more like a touring bike with flat bars and derailleur gears; these are 5-10lbs lighter but have more exposed transmissions.
One feature that may suit your wife is a ladies 'button saddle'. This has no saddle peak (so won't suit if someone rides out of the saddle so well) but it does allow easier riding in skirts and more importantly perhaps it allows an easier slide forward. Some riders who are a little nervous about being able to put their foot down find this a significant improvement. [BB heights do vary a bit but IME few riders are truly comfortable (or efficient) pedalling when the saddle is set at a height that allows a foot well down when in the saddle; arguably if the BB is low enough to allow this then the bike is potentially dangerous because you can't turn and pedal at the same time.]
I know of a dealer in Cambridge who regularly buys good-quality used machines in the Netherlands; he will source what you want for you, (and if it doesn't suit he'll sell it to someone else). For £200-£300 you can have a really nice used machine that would cost at least double this new.
cheers