Mick - only close the dispute when the money is in your hands never before. In fact before it gets to 45 days, make sure you escalate the ebay dispute in paypal to a claim so he cannot get away with ripping you off. Even when he has done this, still give him negative feedback but keep it factual. What a jerk! It sounds like on the postage fees he's hiked the actual postage cost by enough to cover the ebay and paypal fees out of your pocket. People like this should be removed much quicker from ebay.
I had a similar situation a year ago but through a ducati forum. A member offered to sell me some parts which I paid for through bank transfer. He then ignored me for three months until I threatened to take him to court and a refund appeared. Same username was on ebay and he was getting 20-40 negative feedbacks PER DAY ut it still took ebay a year to remove him. Sadly, as long as they are making money through sales I don't think they care too much about the integrity of their sellers...