how to get rid of bamboo which is taking over the garden?

Hi, welcome to GoY, if it's a well established clump. you've got a lot of hard work ahead of you, first step is to get the canes cut down as much as you can, then try getting a sharp spade into the ground as deep as you can, when you get tired of that, go and get a mattock and start swinging the blade end at the root mass like an axe, you can use the pointed end as well, to try and break up the soil around the clump, and just keep going, {if you know someone with a j c b ask them to dig it out for you, a lot easier}, you can also have a hose pipe handy to try and moisten the soil around the roots, but hard work and perseverance are the key ingredients for this job, Derek.