Thanks John,
I've pm'd Steve with a drawing of the existing pond and he's kindly offered to work out what I need.
I plan to have an inner block wall, an outer granite wall and fill the space between the walls with concrete. The inside will then be rendered to the same level as the existing render, then the complete interior fibre glassed.
Probably overkill but it'll look nicer and there wont be any risk of leaks where the new wall joins the old surface.
Just need to ensure matron has all the equipment she needs to complete the task
