I don't suppose you realised that I was being a little tongue-in-cheek when I suggested Redditch, Milton Keynes and Welwyn Garden City, did you?
Now, Cambridge. Do you really think that Cambridge is readily accessible from, say, Carlisle or Leeds or even Bristol? Cambridge is not on any major transport axis and, for Bristol, the great lump of London is in the way. And anyway, Cambridge is already fully occupied in being one of the world's major university centres. Just think about the struggles for resources that would occur if academia had to share the place with Parliament.
I also think that you were considering the need of Parliament to be in some historic and visually attractive location. Are you confusing the function of Parliament with the magnificence of the Palace of Westminster?
Parliament needs good communication facilities (of all kinds), it needs good technical support, it needs to be freed some from some of the shackles of history and tradition. It also needs space for accomodation and support services.
I think that Milton Keynes would be a superb location for our national legislative assembly.