No, it's not legal, but it's a tax thing rather than health or anything like that. You have to have a distiller's licence (also known as a rectifier's licence) and be able to demonstrate that you are a commercial producer intending, with some exceptions, to produce at least 3200 pints of the stuff. Licences are issued by the tax authorities, HMRC. As a producer you have to account for the tax payable on the booze and as this tax is an Excise Duty, failure to hold a license and hence to account for the tax falls under criminal law (unlike income tax which is a civil law responsibility).

That said, people have been known to get away with it.

Aye, it's the same here.  Home distilling is pretty safe if you're not an idiot about it, so the laws are mostly for tax reasons.  Of course it's not really strictly enforced, nor could it be -- anything you need to make a still is also used for regular home plumbing.  If you keep your mouth shut you're fine.

It's got the same kind of status as home taping: nominally illegal, but all the the kit to do it is sold legally all over the place. There's a getaround, too: it's legal to distill and store up to 500l of ethanol biofuel.