Cycling may make some folk who know Milton Keynes think of the redway system. Not my favourite way of getting around though. Lots of glass, lots of punctures and most of the redways are not very direct. The signposting is very poor and in some areas non existent. They are good for parents with children to get the kids used to handling a bike but that's about all. Fortunately there are some decent fairly quiet lanes not too far out of the city. Pity the trains aren't more cycle friendly then there would would be so many more options.
If your travelling farther south how about getting in touch with 1066 Cycling Club a very pro-active club in an area of outstanding beauty. I'm biased because this is the part of the world that I come from. Take a look at the photo gallery.
If you fancy a long night ride how about the Dun Run? I have just done this 120 mile ride starting in Hackney and ending up in Dunwich on the Suffolk coast. It's unsupported but there is a food stop just over halfway at the village hall in Lavenham. The queue was horrendous so I found a seat and snacked on my own supplies. I was getting cold by then so decided to grind on. I got to the cafe on Dunwich beach at 20 past 7. It was bright and sunny but felt pretty cold. Follow this link for more information.
These are some of the local cycling groups which I know and cycle with:
be warned that at present the local Ctc rides are a bit fast for the inexperienced rider