Hi Jane
I'm going to see whether this Harmer fits in with my lot or not and I would advise the SFHG if you have Sussex ancestors and now they have this online access to parish registers for members only it is even better. Currently it is mainly baptisms there, with burials and marriages to come and I have found stacks of baptisms I needed already.
What makes it somewhat easier than going to the record offices and looking through transcripts is that being a database you can search on a name across parishes. Very very useful.
Kerry