Some famous gardens may take a little work to get to, a bus ride and/or a train ride or even an overnight stay, do not despair. There are many beautiful gardens within London that are even more accessible and are as pretty albeit not as huge as those outside London. This is the Chelsea Physic garden and is quite beautiful and is one of these gardens in London that I'm referring to. Besides there is an organization called the NGS and every year they publish a free (a donation may be required) booklet where they list all the private gardens that will be opened to the public. They publish a roster, addressees and charges if any to see them. The booklet maybe picked up in tea rooms, hotels or book shops.Peruse through it and see which gardens you'll be interested in. The most important thing about visiting London is to learn the transit system and invest in an oyster card. There are always friendly staff in every underground system to field any question you may have. I've met many Australian visitors who refuse to learn to use the underground and therefor had to walk miles and miles and get lost. What a futile idea! I love the underground and I love my oyster card. You can surrender your card at the end of your visit and get back whatever money you have left but I keep mine for my next visit. Its like I'm a local!