Should have mentioned this. A bit of all the first 3 - not scoring enough is the definitely the main problem, among the worst in the league for goals scored. Xg is not very high and scoring rate is a little below that. I think possession is fine but I am exposed on the counter. Conceding from crosses was another weakness, I have bought taller centre backs to combat this but presumably still giving away too many quality crossing opportunities.
Having read some more of the guides on this site since posting, I have made a couple of adjustments and this https://imgur.com/a/j72rt6H is how I'm currently setting up.