Having lived in all three, my personal choice would be a toss up between Oxford and Reading.
Oxford - clearly a more beautiful place than Reading, lots going on culturally, lots to do in the city itself. But about an hour from London. by bus or train. Fearsomely expensive.
Reading - bit of a dump (though I have a great affection for it, it's almost like a bit of the gritty north transplanted down south, and I grew up in the north so like that sort of vibe). But - here's the great thing - half an hour on the train to London, so you can do things like go to concerts in London and still get home. Marginally better transport links too. And cheaper.
Since you say you'd be living in a village outside the town itself, there are lots of really nice little villages just north of Reading (though that rather undoes the "half an hour to London" advantage).
(Apologies to the inhabitants, but Cambridge doesn't float my boat, personally. I can see it's beautiful, but in a way that makes me think of painted scenery flats for theatre, rather than a real place. It's also too small - if you took the university out of the middle it would disappear. And I always hear Rupert Brooke's "for Cambridge people seldom smile/being urban, squat and full of guile" - unfair I know, but I just didn't warm to the place).