Trouble with most of the hotel carparks I tried, they have swing down barriers and you need to pay lots of money to park in there. Myrtle avenue is good, and free, and if they're coming in at the other side, 27R, then a brisk walk over there is in order. Another option which I did once, if you're coming down the A4 from London, instead of turning left into the perimeter road, there's a pub just there on the left hand side , can't remember the name, park in there, go have a nice pub lunch and a drink, and then as customer, leave your car there and go for a stroll to wherever your going. I asked once, and the barman said if you've eaten and drunk here, as a customer I don't see no problem. Worked out well, and I had a nice pub lunch inside me !