You can do it yourself. All the leather sections are available from the dealer, as are the foams. Did mine recently and it's very easy, if time consumimg. Got mint US bases and bolsters from a chap on here and bought the backrest and torso bits from VW. £75 for back/torso foam and £350 for leathers. Costs about £700 to fully rebuild a front seat with all dealer supplied sections. Weirdly they don't sell an entire seat, just parts of it.
If you mean reupholster in a different material / colour, there's a good place in Colchester.