Thanks John regards the SPD. ON the tails issue I am using a gland and I would have space on the right hand side of the CU to enter from the underneath my only issue is that it is a MK Sentry CU which unfortunately unlike others is handed in respect that the main switch has to go to the left hand side. This means that I would have to route the tails across the box. The job might be made easier if I am allowed to strip the outer insulation just past the gland to make bending the 25mm2 cables slightly easier, however I do not know if that is permissible as I have only ever seen tails fully sheathed almost to the main switch?

Richard