Neat 100 litre water buts at Argos

[preservefreak]

or you could get a couple of these Mandlaka:

http://www.ebay.co.uk/itm/Water-Butt-200...2321986906

you could have them put away until trouble looks to be on its way, get them out and let them fill or even prefill with a slow hose at night while you have running water.

not a permanent solution, they obviously won't last as long as rigid thick butts but they could bulk out your storage for the first year of a crisis or until things quite down long enough to replace them.