For those who come under Southern Water.
With regards Southern Water. The measures coming into effect on April 5th DO NOT affect any business use of water. I have also phoned them and I can carry on using my RO system even if it's connected via a hosepipe.
http://www.southernwater.co.uk/News/latestNews/default.asp?aID=76510414&year=2012&month=03Drought forces water restrictions in Kent and Sussex - 12/3/2012
Southern Water is to bring in restrictions on water use for the first time since 2005/6, following the second driest 12 months on record.
From April 5, the company is restricting the use of hosepipes and sprinklers in Kent and Sussex. The restrictions apply to customers whose water is supplied by Southern Water and primarily cover domestic, not commercial, use.
They also include:
Watering of public parks, gardens and allotments
Filling swimming pools, paddling pools, ponds and fountains
Any apparatus connected to a hosepipe