Don;t know but Google it if you don;t get answered. DH goes to a golf club and they start teaching kids from 7 (it's not in London though) although would take really keen ones from younger age. DS is interested and will be 6 soon - strike while the five iron is hot!
Dd2 did golf lessons with a pro in a group for a time when she was 5. She loved it, and would like to take it up when older and has given something else up to free up time. I did check before she started, but that was mostly because she would be doing amputee golf and I wanted to make sure she wasn't going to be completely out of her depth in an ordinary class. She loved the driving range!
DeWe - my (adult) friend is an amputee golfer - he lost an arm in Iraq. He's very good and is mentoring other amputees - mostly ex-forces but not all - really popular and fantastic for self esteem. His daughter (who's 13) plays too. Definitely a side of golf that blows away all the stuffy gents' club image - although that has a certain truth to it too.
Definitely not to young to have some lessons - my daughter has just been giving golf coaching for 4 years olds at nursery. She's been using equipment specially designed for youngsters, but at 5 there is no reason why they can't start with proper golf clubs and balls.
It's worth checking out members clubs as well as public courses as you often don't need to be a member to attend lessons.
Ds started at 4. He's now 7 and has private lessons every other week (supposed to take him to the driving range every other week but that doesn't always happen).
It's his absolute favourite activity. We went the the Open last weekend and he loved it. He plays at a very friendly club but isn't a member (and neither am I). No pressure to join either. Ime not all clubs welcome children that young so you can end up with lessons on the practice range and nothing else.