I had a similar problem on my old Polo 6N2 which developed at around the same mileage. First thing I did was to install a brand new set of ignition (HT) leads, as I noticed one of the connections onto the spark plug was not very tight and they were looking a bit worse for wear. It completely fixed the problem and saved me a lot of money in the long run - had plenty of other things lined up to check but thought I'd start with the cheapest option first. Worked for me but obviously might not work for you mate.
Might be worth checking the connections and if all else fails get a new set on there - can't do any harm.
