Thanks for all the help
You guys are absolutely right, my fuzzy brain had forgotten that wool is heavier than plastic
I had a closer look at the yarn I was using. It really didn't LOOK all that different, but when you held it up against some of my other stash ones and squished and pulled it, yes it was thicker.
I have ditched the navy blue and found a dark brown. 3.5mm hook and a couple less trebles and I'm away.
I should also have done the swatch the way the pattern is, which is one row tr, one row sc, that holds the sloppy top of my trebles together.
Once I got to the shells it seems OK.
And I leant a lot along the way, which is COOL
Would like to know more on wraps per cm though, not heard of that one?