And so it begins... you realise that the person who mapped your area missed a few details. The area around your kid's school doesn't seem quite complete.... What? Nobody's mapped *every* lamppost in Peterborough?? Good luck!

You might be interested in http://openstreetview.org/ too, I'll have to take a look at archive.org to see if there's any way to work with what they're doing.

I'm a little disappointed you haven't made one mentioned of what existing coverage there was, only what's missing. There's definitely a lot to be done in the North, and certainly bits that need polishing in the center, but there's also loads that has been covered both in the city centre and towards the south of the city.

Looks like Virtual Earth and Multimap both have some basic roads in the area:

http://johnmckerrell.com/map/#t=4&lat=36.83374&lon=28.64303&zf=14

http://maps.live.com/#JndoZXJlMT1EYWx5YW4lMmMrVHVya2V5JmJiPTM2Ljg2Mzk3MDA3ODQxMjglN2UyOC42OTYyNDM1ODQ0MDg5JTdlMzYuODA2MDI5MzEyNDI3NyU3ZTI4LjU5OTc1NjI0MDU5MTk=

I did some mapping further down the coast around Kalkan earlier this year myself too, lovely area :-)

I think postcodes tend to be considered fairly low priority in OSM, but I always add them when I can. In my city all the road names show the first half of the postcode so I also add that to pretty much every street I add. Keep putting them in, they'll come in useful eventually and you'll only kick yourself for the times you didn't bother!