In reply to Daniel James:
I was in exactly the same situation earlier this year, plateau'd at v4 with a couple of v5s. I normally climb at the reach and the biscuit factory / arch. I did the following:
Booked a 1-2-1 session with a Gaz Parry to get some tips - gave me an idea of weaknesses and how to move forwards.
Focused on beastmaker sessions on days I can't climb (I only usually get to the wall once or twice a week).
Spend more time reading problems and mentally doing the moved before wasting energy on the wall.
Get a project mentality, do all the individual moves on a hard problem, then work on doing first half/second half, then put it all together.
6 months later, I'm now consistently doing v5 and have done a few v6 problems.