How much water can you collect with a water butt?

A lot.
My other half has set our new Wilko's 250 litre water butt up, which is superb.

There are just three problems with it.
1. The lid doesn't quite fit on properly (possibly needs a bit of filing down).
2. The tap has a permanent drip of dozens of drops per minute (we've contacted Wilko's, as no one complained about that in the reviews), and

3. After just 3 days of May rain it's already full!

All 250 litres! And I thought that it would take weeks of rain to fill it.
That's what happens when you collect rain from a 16 x 9 ft roof I guess. I suspect some of it ran off, because it looked like it had reached the very top. Our current solution is to use the water up on the garden whenever it even needs it a little bit. We may ultimately need a second water butt.

The back of our water butt (and I would think any water butt) has a T-section on it where the water comes in. All you need to do is take the cap off it and attach it to the T-section of the next water butt with a hose.

Currently, the water comes down the down pipe into the diverter.

It fills the water butt until it's full, then any extra water simply continues on along the down pipe. Unfortunately, our down pipe doesn't end anywhere that can take a lot of extra water. We simply added bends in it to funnel it away from the shed to between the water butt and the compost bin.

From there, it will gush out over the garden instead of making the shed base subside or water-damaging the fence or the shed. Which isn't bad, but it's not ideal either. I guess we'll soon find out how much damage water gushing all over the vegetable beds does.
In other news on fixing things, my other half also came up with a solution for how I can leave the greenhouse door open to keep the greenhouse cool. The door being made mainly of a huge sheet of glass, we didn't want it slamming and breaking in the wind. What he did was attach a cabin hook.

It's 30 cm long and I hook it on when I want to keep the door open to cool down the greenhouse – like today, when it got to 33° C, even with the door open.

I bought a temperature logger to find out how hot and cold it gets. I'm not yet sure what I'm going to do with the data, I just feel like I should have it. The data logger records a temperature reading every 30 minutes (or whatever interval you set it up for) and you can plug it into your computer and download the data from it. Alternatively, you can just press the play button and it'll show the current temperature on its screen. Frighteningly, in the two weeks I've been collecting data from 7 to 21 May, the top temperature was 43.3° C at 12.57 pm on 10 May and the lowest temperature was 2.2° C at 5.57 am on 10 May. I wasn't expecting it to drop so low, but on the plus side it didn't freeze. It's strange that my high and low were on the same day. It makes me wonder if something happened to distort the data or if it was just a very cold night followed by a very sunny day.