Did you realise that you have offered to deliver this £5k cattery by 1st class post for £3.85? I suggest that you revise the listing to remove this, or someone may try to hold you to this!
It would be safer to try to get the buyer to pay in cash on collection, although if they insist on paying by some other way eBay will require you to accept this. There is an easy scam by which buyers can collect the item, then engineer a chargeback. Without proof of posting or delivery sellers have no defence against this. You would need to get proof of collection, ask for ID, signed collection receipt, have a witness, take a photo etc. This doesn't prevent the scam, but should deter most buyers from trying it.
