Yes it does seem that is what has happened, i spoke to the vet on saturday and went in, she tests her kidneys and she was in the high section, but said not worryingly so, we got some anti biotics and went home, i have been back for a check up today and they have kept her in - they have re-tested the kidneys and they are getting worse.
She is now on a drip with 2 lots of anti biotics, my bill so far for what the metacam has caused is 300, the vet has put a call into metacam and they have made a note and said that yes this can happen but in rare cases and she must have had an underlying issue to cause it!
I have told everyone i know who has a cat about this and to be very careful!
Thank you for the information on your website - it may have saved my cats life although it is still early day