Nice system - I have the same except a Beocord 2400. The Beogram is the most valauble bit and the Beomaster would be next. Condition is everything though. In perfect condition, the Beogram might get £200, the Beomaster up to £150 and the speakers (if S45-2s) £75, especially with stands. The Beocord is essentially worthless - appalling thing to say as this is a very good deck, but true - and the furniture is quite difficult to get rid of!!
The system will need servicing - capacitor changes and new belts - but in good condition, will blow away most modern mini systems. Keep it!