It's maybe a tad short at 4 m. You might find that you need step ladders to reach some roofs. I find I sometimes need them with my 5 m pole.
Apart from that, it looks fine.
You'll probably need about 10 m of 5 or 6 mm tubing to go between the garden hose and the pole. You don't want to be dragging garden hose around with you as you work. It's double the diameter, so 4 times the weight due to the water! And you need the connectors to join the 12 mm hose to the 6 mm hose.
You might also want to fit a tap in the tubing near the pole.
Phone those nice people at cleaning spot <<http://www.cleaningspot.co.uk/index.html>> and they'll sort you out with any extras you might need.
And good luck to you.
The overarching advice is:
Keep it simple and keep it neat.
Of course, you need to clean the side windows afterwards. So you'll need an applicator and squeegee plus a bucket to keep your solution in. Use washing up liquid. And a couple of cloths to do the detailing and wipe the frames.
Oh, and one more thing. I wouldn't use a conector to a kitchen tap. If the connector comes off the garden tap, you get wet soil or flags. If anything goes wrong in the kitchen, there's an awful lot of damage can be done by the time you've realised what has happened, got down your ladder (and it will ALWAYS happen when you're up a ladder as far from the kitchen as possible) and dashed in there to turn the tap off!
No outside tap - no take the job.
