I'd go for a basic D90 as a good mid range camera.. Have a look at this web site very good for locating the best price.
http://www.camerapricebuster.co.uk/cat4.html
Two tips
Rear screen resolution - try and get over 900k pixels - makes reviewing pics SO much better and easier.
Sensor - when taking low light shots (without flash) you raise the ISO on the bridge/entry DSLRs you will introduce a lot of "noise" in the picture - so Mid Range cameras are able to go into the 000's before you get a bad nigh shot.
HTH
Tone
