Sorry for the late reply guys, but here's an update;
On Monday, the engineer came (he came on Thursday aswell but I wasn't at home) so on Monday he came and had a look. He says that the crack is very minor and it won't be needing a replacement chassis till it affects anything. Err k.
He did, however replace the ball hose and took the yolk assembly etc off and it all went well. He noticed that the wheel of the cleaner head was wearing out so he sent me another one which arrived 2 days later (today) and I also demonstrated how the bin wouldn't empty, so a new bin got sent out too, the machine looks so pristine! I will give it a clean up and take a bunch of pics to look back on in the future
I will use the old bin but use the new one maybe once.
Oh and PS I have to send back the old cleaner head, WTF?!