I just won an auction for £27.21 and my max bid was £29. I am being charged £29 and on top of that the postage has increased after i won the auction.

Your maximum bid included the buyer protection fee, that's what you won it for. £27.21 is just ebay showing what the amount less the fee is. It's not your actual bid amount. Postage can't increase after you win, can you show us where you are seeing this?