OK now being the determined logical person I am I wanted to fix the pool myself so logic says if there is air in the filter I need to force water in and push the air out. Makes sense. But where and how to force the water in? Firstly I tried directly in the pump skimmer but this seemed to be forcing air in too. Think ,think think and thanks to the magic of Google I found a piece on how the pool professionals put a hose with and inflating balloon like cuff up the pipe from the pool skimmer box to force the water through. Now I don't have an inflatable cuff but the article then went on to suggest jamming a thick sock around the end of the hose to create a seal. So one hose pipe, two towels for kneeling on, one pair of sports socks, two adults, a child, lots of on off with the tap and repositioning, half and hour and very aching arms later the pool is fixed. Hooray.... I love it when a plan comes together.
I've reconnected the pool cleaner, put the chlorinator up higher and left the pool to run for the next 24 hours. fantastic. My pool no longer sucks - well it does but in the right way this time.