Thanks JRV!
I took it for a good thrash down the motorway (Freeway?) yesterday, and around some country lanes and the problem seems to have gone away.
I tell you what, these cars really can take your breath away. My car is nearly 30 years old, and still drives better/looks better and performs better than most of the mass produced cars that clutter up our streets. They may be tempremental fuel guzlers - but what a way to go