Correction - hardness was 1200 ppm! (Sorry my typo)
Yes, the cell is spotless.

I didn't believe that with low cna no chlorine is produced, but thought I would check just to be sure

I have come to the conclusion that it will be cheaper and far less time consuming to go back to chlorine tabs in a floater. I should also save on acid as when the SWG was working I was using a lot of acid. I think this was caused by the generation process itself rather than just having salt in the pool, but I guess I will be finding out for sure!