Oh Honda Jazz, how I hate your tiny little sparkplugs and their over-generous number.
Two plugs per cylinder mean that half of them are hiding down the back. As they're all buried beneath plugtop coils, none of them are exactly easy to get at.
The fronts are accessible, but the (fragile) plugtop coils are stuck in place like the distributor of a winter-rallied Mini. They have to be pried out with my claw-like walnut-cracking fingers, hopefully without pulling their tops off.
Removing the plugs needs a plug spanner with a rubber insert. Putting them back in needs a spanner without an insert, otherwise it's stuck more to the plug than the square drive. You can of course haul them out afterwards with a nose hook, but it's easier to just have two plug sockets, with and without the insert.
Now the fun starts, the back row. Give up, abandon your fingers and evolve some tentacles. You're going to need them. At least the coils probably come off, but you can forget about even being able to see the plugs. Phone the Snap-on van and order one of every sort of 3/8" drive extension and UJ they have. Did I mention that the bonnet seal and even the windscreen are in the way? I did most of this with a spiral flex drive, but it's not enough torque to break the old plugs free.
Allow an hour to do it. It won't take all that long - you either have the bars to get to the back ones, or else you don't. At least they don't need changing very often