terenz,
So much for creative flying, huh? I'd sure hate to toss the already purchased tickets but am beginning to think that may be the solution. I'm curious, why do you think r/t would be less expensive than o/w?

How much time would you estimate it will take upon landing to retrieve our luggage and be on the road if we hired a car and driver? The price I've been quoted so far for a hired car is £69-£84, depending on luggage, so it may well be worth tossing the old tickets and just taking our time with the rail or bus system to get to LHR.

We are flying from Rome on July 4th...thanks so much for your help!!