Welcome to Beoworld! Many of us here have a keen interest in the older B&O kit.
The system you have is definitely too good the skip! You have a good system that deserves to be preserved and listened to, not worth an awful lot of money but one that compares well to a lot of newer kit. I am pretty sure you can attach a CD player too. Is it you system or have you inherited it?
Rough estimates for eBay proces:
The Beovox S45-2's are good speakers. If you try them head-to head with any more modern speakers you have you may be pleasantly surprised! If they are in good condition they should go for about £20-30 on eBay. It will help if you have the original stands. If you end up keeping them it is worth replacing the electrolytic capacitors in the crossovers as that can work wonders for the sound.
If the Beocenter is in good working order you will proably get around the same, possibly a little less as the model is not all that wekll known.
The turntable value will depend of whether or not the stylus/cartridge is still in full working order. If it is you will probably get another £30, if not maybe £10-20. However, if you list the cartridge and turntable separately you can expect £30-70 for the cartridge (depending on model) and £10-20 for the turntable. If you do list the cartridge separately security mark it in some way before you post it to the succesful bidder, some scammers will send their broken cartridge back and claim that it is the cartridge you posted to them!
Simon