I originally booked my transfers with another company that makes sure they are first on internet searches. After doing so I checked their reviews. So glad I did - they had horrible feedback. Searched some more on travel review sites and happened upon 12 Transfers. Excellent experiences both ways from Heathrow to Southampton. Very courteous and accommodating. Their communication is outstanding. You get emails confirming your trip. Once you confirm you get driver details, including driver name, a picture of him/her, the car you'll be in and the license plate. Can't recommend them enough.