Thanks to Barry and Nozzi for the replies. Reading all this and the links it looked to me that the safest thing would be to replace it with a gel battery again. The only suitable I found was the G80 (ES900) Exide Gel Leisure Battery 80 Ah. Not cheap, £180 fromm Alpha batteries or Tayna.
Thanks Barry & Maggie. I did hope that I may not be alone with this problem. With hindsight, and if I had read the thread and your wise advice, I should have lubricated, it was getting stiff.