I have been 'tasked' with getting tix for next year's CFS.
Have been on the website to look at prices and it strikes me that it'll not cost a vast amount more for me to get a membership and buy 4 tickets on that- BUT is it advantageous to go on the first 2, members only days or not in terms of crowds?
I'm a member and always go on the first Tuesday. I've only been on a non-members day once, second trip in the same year, and I did notice a difference in the level of crowding. It felt busier, more touristy, and the gardens and displays weren't as fresh and perfect.
As a member you can only buy two tickets for members days at Chelsea, but I think you can buy more for Hampton Court.