Don't take the grades too seriously. I still cannot play much of the grade 2-3 material, but I have been learning Scarlatti sonatas level 5-6 and though they need work, they are not impossibly hard. I think the difficulties there are manageable with work even without much playing experience. If you really like the piece, practicing a lot is not unpleasant 
Much of the romantic and classical stuff is different (at least to me), I feel I would need more basic skills (and physical ability/bigger hands) to even get started on them.
Yes, I could play one of the Scarlatti sonatas years ago. Can't remember which one though. It took some work, but it was effort well invested. In this respect Scarlatti resembles Bach: the music is interesting enough that one doesn't tire of it, so it is well worth learning.
In fact, this brings me to a question. Years ago, when I taught myself, I got hold of and played exam pieces, in order to pace myself and get some idea of what I could and could not do. Once I could play a set of exam pieces in one grade, I would move on to those of the next, and so on.
In the grade 4 set I ran into the minuet from Bach's French Suite no. 3. It took me quite a while to master it, but it was worth the effort. However, it always bothered me that the exam book didn't include the trio - one after all usually plays a minuet with its trio. So now I want to remedy that oversight, only to find that the trio is hellaciously difficult. Or is it? Perhaps I'm just rusty with learning new Bach pieces.
I wonder if anyone can tell me at what level it is. If I can play the minuet, should I be able to play the trio as well, or is it in a whole different league? And how does one finger all those voices? Is it for example accepted practice to play one voice with different hands, or should one use the same hand for a voice throughout? (If so, the piece seems to include quite impossible stretches!)