So, i captured them during the recent mild weather and before it turns cold again.
I still want to hibernation to occur but in a more controlled way......somewhere that has easy access to the turtles.
Deciding to use a plasterer's bath, some insulation was in order and 50mm thick poly foam boards proved to be ideal. One pack of these panels is just enough to completely clad a standard plastic bath.
It is shaped easily using a serrated kitchen knife, much better than normal polystyrene and a denser material too.
One board goes underneath, two others are cut to suit the sides, it can then be held together using duct tape.
Finally the bath is covered with a portable plastic breathable cold frame as extra protection against the elements.
As i have said before, at least this way i have some control and easy access to the turtles. I may only use the lid during severe cold spells.
I will check this set up against an unprotected bath nearby and will have the option of bringing the turtles inside should it not prove successful.