Windsor Cars

Excellent company.
We have traveled from Windsor to Heathrow with them several times.
Clean, new cars (black Mercedes), professional driver in a business suit.
Polite, friendly, on-time.
Reasonable price IMHO; but that is subjective. It's for each person to decide if it fits their budget.

I used them for a Heathrow to Windsor a couple of years ago. As Rebecca described.

We used them a few years ago. Pickup at Heathrow was easy--they called us and told us where to find the driver. It helps if you have a way for them to contact you when you land. Upon arrival in Windsor, we needed an ATM, and the driver took us to one a few blocks from our hotel and waited while I withdrew cash. He was very polite.

Thanks all! Sounds like a reliable option.