We used Heathrow Airport Parking In September 2019, when we were going for a weeks city break to New York. Had it been just me travelling I would have used the train or underground to get to the airport, but as there were four of us it worked out a lot more cost effective just to drive and park.
An added bonus was that we were very near to our terminal, meaning no waiting for a transfer coach, and we didn't need to hand over our keys and entrust our beloved car to someone else to drive and store goodness knows where. Just present our printed out details to be scanned by the lady In the kiosk, park and get ready to enjoy our holiday.
Because I was able to pre-book nearly 6 months in advance I acquired 8 days of parking for just under £70, which I considered good value, especially when the thought of dragging suitcases onto trains or undergrounds flashed In my mind.
On returning from our holiday our car was just where it was left, ready to take us home.