Just noticed a reply in Amateur Gardening magazine to someone asking about watering with tap water & they say to add Greenacres sulphur to the watering can for lime-haters such as blueberries, camellias etc. You dissolve 1 scoopful in 1 gal. of water. You can buy the sulphur mail order from Greenacres Horticulture Supplies, PO Box 1228, Iver, Bucks., SL0 0EH. Tel.01895 835235 or log. on their website which I've put a link to below but which appears to be undergoing maintenance at the mo. You can probably buy it from some garden centres as well.
www.greenacres.eu.com