Stitches as per size are (90:102:120). I've counted numerous times and get 102 each time so no error there. Row 2 is starting with one stitch of contrast as pattern states (1 contrast, 3 pattern, this repeated to the end), and ending with 1st stitch of another block of 3 pattern. I can't understand what's going wrong
Yes, you're right, that's the way row 2 should end, with an open square and one filled square of the set of 3.
The easiest thing to do may be to block off a 6 stitch repeat on the chart which will work for your size. If you start this repeat on the left at the 1&2 line and count 6 blocks over to the right, that's your 6 stitch repeat. So for row 3 you read from right to left beginning with 3 open squares, a filled square, then 2 open squares. You can then continue across the row ending with a filled square and 2 open squares.
Use the chart too to make sure your stitches are lining up correctly with the row below.
Hi again, sorry it's taken me a while to get back to you. I continued as you suggested and managed to finish the hat Thank you very much indeed for your time and advice! Wish I had posted on here earlier, this is a great site