Dean presented the following explanation :
I'm guessing the grinder is easiest and fastest. How safe is it to cut up
the tanks with an electric grinder in the loft space (sparks)? Is it viable
to cut it up with a jigsaw?

A jigsaw would just about hack it, but I would go with the angle
grinder. To contain any sparks hang old curtains or bed sheets which
have been damped around the area. Get someone to watch for possible
signs of fire, you can't do both and have an extinguisher to hand
ready.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk