I have been quite obsessed with garden size since we started looking for a house...especially as the photos make them look so much bigger than they really are, and they don't tend to have measurements on them.
Anyway, in case anyone else is similarly obsessed, I've just discovered that you can take measurements on google maps! You drop a pin, click on the location and then there's a button to take a measurement. I've had great fun comparing all of the houses we looked at! I'm not sure if it's 100% accurate but it's close enough to get an idea.