Hey, welcome! 600 is a fantastic bike for London and the mileage isn't a problem if it's been looked after. Make sure the cam belts have been replaced within the last two years and the oil changed regularly etc and it will be fine.
I'm off on one here, but these guys who say Ducatis are unreliable - what a crock of sh*te. They're mostly people who buy new or nearly new J*p bikes and have never had a Ducati but know a mate of a mate of.... who had problems with his because it was 15 years old and he/she never maintained it or maintained it themselves badly. Ducatis seem to last longer than J*p bikes cos they're cared for and are still good bikes whatever there age. Any old bike will have its problems, just like old cars will. There you go - I'm done.
