I like the look of the vintage Dawes but am not sure they would be adequate to hand the hills I will be tackling - albeit after my fitness improves.
I started a thread here asking about Dawes Heritage bikes, then came over here and read this. The Duchess and Cambridge have 7 gears, personally I'd prefer to ride steeper hills on something with a few more gears. They are very pretty bikes though, I'm hoping to get one as an errand bike.
My suggestion for you would be to try a Specialized Vita. Mine has changed my cycling out of all recognition, it's a such a good fit for me and so easy to do the miles on compared to my first "comfort" hybrid. It will take mudguards and a rack, and you can add slightly chunkier tyres if you'll be riding on towpaths/less smooth surfaces.
eta, the entry level Vita is gbp370, without mudguards and rack. I'd also recommend visiting your local bike shops, they are invaluable. I did a basic maintenance course at mine and learned how to replace tubes, fix a broken chain etc - I'm far more confident now.