Commuting to work on the bike is a good way of fitting in miles. It turns your commuting time into useful time. You can also use the bike for getting to the pool, or shops. If your bike is fitted out for winter, with lights, mudguards and plenty of reflectors, it is easier than it sounds.
Hills are good for strength training, but to lose weight, long steady miles are probably more useful. I tend to back off hillclimbing in winter and find flatter routes; it makes for easier temperature regulation, but go for every hill in summer.