Let's say your maximum requirement is 80A at 240V, or around 20kW. You
need to size your UPS appropriately - one of these should be fine:
http://www.keysource.co.uk/ups/datacentre.asp?id=75

The one you suggested is 3 phase, so might not do the trick in a domestic
situation.

Hmmm. Something like an APC Symmetra LX 12kVA would do, if you take any
electric cookers, heaters and showers offline. Costs about 5,525 though. ;-P

OTOH, if you shed load and don't run the tumble dryer, you'll be able to
watch TV/computers etc. for hours.

Christian.