Ok, go the FORUM PAGE on RootsChat. Scroll down the page to ENGLAND then click onto SUSSEX (which is where your grandfather died). Then click on NEW TOPIC.
As a suggestion, put your grandfather's name in the 'subject line', along with looking say 'looking for grave'.
Then in the main body, put in as much info, ie his birth and death dates, along with wife?'s name.
The more info you include, the easier it is for someone to help.
Good luck