Great idea to do this. I would suggest that you put things in little 'workstations' that you can carry around, if you need to, as much as is practical. So maybe all your basic gardening stuff like trowel and gloves in a small plastic crate that you can bring out into the garden when you work... Next all the little 'diy' things, sort of like a sewing/mending basket, ie nails, hammer, picture hooks, stanley knife etc again in a small plastic crate so that it's easy to take to wherever you're making a repair. Try to group and place sports equipment so that it's easy to get out an use and any related stuff to that particular activity is near it and accessible. When you've worked out what you want to keep and how you want to store it, you might need to install some shelves or a peg board for bigger or less often used tools etc. Hope this idea helps!

As with most addictions, people are very good at ignoring how bad the disadvantages of the habit feel. Sometimes just acknowledging how much your clutter trips you up is enough to give you a push in the right direction, but you're right, if it's got this bad, it's going to feel worse before it feels better!

I find that my desk stays tidy all day and I focus much better on whatever I'm working on if I stick to doing one thing at a time, and put all the papers etc relating to that one thing away as I finish it. Really helps me to feel I'm powering through work, and keeps my energy levels and work satisfaction levels up too! But, if you're going to do this, having a good system to make sure you check in with everything you're supposed to be taking care of without the visual reminder of it being on your desk (nagging at you!) is essential...