Hi, I think you are correct about the path. However there is a caveat. It runs trough a farmers land and care must be taken not to stray from the path and not to drop litter etc. https://www.spotterswiki.com/index.php/London_Gatwick_Airport
I know there is a Gatwick Spotting expert (member "andygolfer") a moderator on the Civillian Aviation Enthusiast website.He is a very helpful guy. Perhaps you could send him a pm for up to date info. http://www.civilianaviation.co.uk/forum/
There are a bunch of very keen enthusiasts like andygolfer on the CA forum who are regulars at Gatwick. They get some great photos and they can give you some tips where spotting is best at a given time of day/year.