Thanks for the reply, unfortunately it turned up it's fins at the w/e. But it had a good long life (14-15Yrs). A few hours after removing the body I spotted a couple of just hatched baby plecos (with yolk sac). The circle of life.
What was the outcome with you fish. I have one that has done the same thing, it (dont know gender). swelled up over the weekend, still swimming around and seemingly happy. It's 14 years old and never happened before.