fuel consumption and other bits

i've just bought a 1982 W123 200T with no service history or any manuals etc. while i am familiarizing myself and getting hold of service manuals etc i thought i would just ask a few questions.
1. fuel consumption seems very bad, it has new tires, and spark plugs look good and clean, any ideas what might cause this? what consumption can i expect in town, and on motorway?
2. excessive white smoke on start up for about two minutes: i see from an earlier article this might be the head gasket going, is there a test i can perform to identify this?
3. does the engine have cambelts or chains, if belts i had better replace them.
thanks in advance for your help