Hmmm... I was faced with this not long after I joined my club.

I was dominating the regular members and when I didn't win it was usually because a visitor was riding.

I decided to stay in my grade til the end of the series to really consolidate my confidence and also to try and improve my racing ability and attitude on hilly courses.

What I did do, however, was to ride up a grade a few times just to "get a feel" for how the grade raced, and what pace they rode at. Are you able to do this? I still got a point because I raced, but even if I had got placed I would still have only got a point because I wasn't in my grade.

When I did move up, I felt prepared and confident (well, kind've )

If you want to consolidate, stay where you are.
If you want to be challenged more, either ride up a grade to try it out... or actually move up.

Have fun making your decision