Is it illegal to purchase sulphuric acid?

Sulphuric acid, intended for use in batteries, is available from auto supply stores.

No i need it to clear my drains..my Washing machine is not allowing the water to drain away, the blockage in the pipe means i have to stand by the water out pipe with a bucket to collect all the water draining out...i hear sulphuirc acid was the best method used by plumbers to clear drains...

I'm not a chemist, but being 'horrified' by your question, decided to look up a couple of websites. I suggest you do the same. It seems sulphuric acid is used for etching iron pipes and also in a copper extraction process, so if you have or suspect there may be either of these or any other metal pipe in your system, steer clear of sulphuric acid. Apart from anything else, it is extremely dangerous to use, and even breathing in a small amount of the fumes could cause permanent lung damage to you and/or your family - such fumes could linger for many hours after pouring the acid into a drain. Also, accidently mixing this acid with another chemical such as cleaning residue could result in the immediate production of very dangerous fumes. Use and handling of such corrosive and toxic chemicals is a job for experts, fully trained in the correct methods, and equipped with the necessary protective and breathing equipment. There are various commercially available drain clearing chemicals, which any decent plumbers merchant can sell over the counter. I suggest you use one of these, but observe the instructions regarding dosage and ventilation very strictly. Whatever you use, make absolutely sure that it is securely stored when not in use. Finally, I am pretty sure that pouring acid and similar chemicals directly into the public drainage system is illegal. Before using them you should contact your local water authority and your local Environmenal Authority.