My new lance just arrived from clean your car and blimey thats a piece of kit. It must weigh a kilo!
Congrats on your new purchase
You can see where your £40+ has gone when you see it in the flesh and you can probably also appreciate why they do a much better job than the karcher one.
Takes it a bit of trial with the dilution and spray adjustments but you'll get to know what is best, after a few goes. Best advice is to make sure you run clean water through it, when you've finished each time (via the pressure washer), as they can clog easily with dried shampoo if you don't. Enjoy foaming.