Ian, theres's far too much unwarranted fuss about ground radials in ordinary
English gardens and back yards. Just lay a few wires, 6 to 12 in number.
beneath a trodden-on, compacted soil surface, with lengths of a few metres,
perhaps 5 to 10 metres, and away you go.

Don't forget to attach to the incoming main water pipe and the domestic
plumbing system if you have one. Also the electricity supply ground. And
then stop! Or stop before then and see how well it works.
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Reg.