Mate either way.
If you're not comfortable with heaps of cash, bank cheque is the best option.
A bank cheque, you pay the money in advance, so the seller is guaranteed that the funds are there.
i.e The cheque cannot bounce.
Whereas a personal cheque, can bounce, if there are insufficient funds.
However it takes 3 days for them to clear (like a personal cheque) quicker if he's willing to pay for special clearance.
Explain that to him and I think he'll be happy, can't blame him for being hesitant in regards to a standard personal cheque lol.