Hi George and welcome to Beoworld.
It sounds as though the belt is overstretched and could even be the original! It would be best to replace it with a new one anyway. I don't know about UK stockists but eBay is usually as good a place as any for new belts (particularly the ebay.de site) there is one listed as item number 350513339564, and another at item 160546869829, both ship to the UK and it will cost almost as much as you paid for the turntable!
The transport screws should always be completely loosened (anticlockwise) when you want to use the TT and only fastened when moving it.
You won't know the condition of the cartridge or stylus until you try it or examine it by magnifying or electrically. It sounds promising though. Again, they (SP14A's tracking at 2g weight) are always coming up on eBay around the world. Is this what you currently have?
As for the lift button cover. If it's missing but was on the advertising photo - contact the seller and tell him it is missing and he should send it to you, otherwise the item is not as shown or described (depending on the wording of the eBay item). I'm sure another Beoworld member may have a spare one somewhere.
When you change the round belt, it will be worthwhile cleaning and lubricating the TT - use a good quality oil as have been suggested on this site many times and DO NOT USE WD40!
Upgrading membership on Beoworld gives you access to the user and service manuals and is well worth it.
Good luck and I hope you both enjoy it.
Dave
Am I ready? I was born ready!