Factor, I haven't sold to Malaysia but I have sold worldwide on eBay from Alaska to Australia, I insist on payment by PayPal for any purchasers outside the UK, and as long as they have paid me, I will mail the goods.
There is no difficulty in looking up postage, this is my bible
http://www.royalmail....53800712&catId=400036 and you can make it clear that the recipient is responsible for any import duties. When I have bought from the USA and the purchase attracts a Customs levy, it's always been me that's paid, never the seller.
All I do is obtain a certificate of posting at the PO when I mail from here in the UK, and even though I have had items go astray now and again, the Royal Mail has always coughed up for the value of the item (less postage) so I can refund the buyer if need be.
If you really don't want to do that then all you need to do is point them to the line in your description which says that you only want to sell within the UK .