Glyn,
Not much comfort I know, but that sounds about right for an ST2 chain. I got mine changed at it's big service with Nelly. The bike had done about 12.5K, so a little bit more mileage than yours (which isn't bad when you consider my bike has a much bigger engine than yours
).
Neil used a Tsubaki chain and Renthals sprockets on mine - cost me around £130 or thereabouts. You'll need to change the lot because new chain on old sprockets = premature wear