Oh my, there couldn't be any more red flags pointing to a scam.
Do not reply to this buyer just block them, and at the bottom of the link below you can block their messages too.
https://www.ebay.co.uk/bmgt/BuyerBlock?
Never reply through private emails, you do not deal with sales through eBay messages, the buyer just needs to, if they were genuine which they are not, to be able to buy from your eBay listing.
Never post to a different address when requested , only to the name and address eBay provide for you on the order details for the item, and this is sent to you when the buyer has paid.
So just ignore, do not answer and block them now.
@lally_k