BSC and drafts can be forged or stolen. Make sure the sale completes during banking hours and call the named bank to make sure it has been legitimately issued.
Look at photo id of the seller - his driving licence or passport. Get proof of his address.
The last time I sold a car the buyer was very understanding and happy to come with me to my bank where the cash was handed over and deposited in my account. I wasn't going to risk forged bank notes.
You are right to be cautious.