In message , at 17:32:48 on Wed, 26 Mar
2008, Graham Harrison
remarked:
On a Sunday afternoon in late July my wife and I will be departing from
St. Pancras station in London via Eurostar. Prior to this we will be
using a rental car for a few days, based in Cookham, Berks.

If you can drop the car off at Heathrow, I think that's the best option.
The Piccadilly line train is approx 1 hour to St Pancras. I can't think
of a faster way.

After dropoff you might want to try going via the new Heathrow Terminal
5, compared to the centrally located T123.
--
Roland Perry