Im sure theyre great for storing water but B+Q made an error of judgement with the British PUblic stocking these things. No-one REALLY wants to dig their garden up to save a few litres of water when theres 210 litre butts available, unless your a window-cleaner of course.
I see they come with a pump, filter and diverter too. Nice loss being made on these no doubt.
Could be fun getting them round the back of properties, bearing in mind the size, have to roll it Id imagine.
You could always cut the top half off and have a ready made swimming pool

Post some pics when you got the machine in to do the digging.
Could be fun.
Good luck.
Matt