What are the requirements for my garden studio?

First of all, I need some space where I can make music without annoying family or neighbours too much. Ideally space where I can have a few friends round so that we can practice together, a space where small groups can be recorded. But mainly somewhere where I could have my keyboard rig set up permanently.

Also, we are short of storage space around the house – so any extra space would be a bonus.

There were some other requirements (warmth, noise control, security and such like), and the ability to use it when working at home from the day job.