Dyson D14 not picking up from brush - poor suction?

Hi there. My dyson D14 has been knocked over, and ever since, the suction around the brush area has been poor. The hose has a lot of suction. It's 6 months old.

I rang Dyson and I've done all the tests they suggest (such as taking the side valve pipe assembly off and checking the suction there - its as good as new there), and trying to vacuum up small bits of paper (they remained on the floor).

I've cleaned the filter and the chamber and the cyclone bit - i got a LOT of dust out. We've had building work done and vacuumed a lot of plaster dust etc up, which I've since learnt Dysons simply dont like! All relevant tubes and hoses have been checked for blockages, and everything is clear.

The vacuum doesnt quite sit level on the floor now - when we use it, you can hear it scraping along the floor, and you can see the marks on the bottom of the motor casing. The seal on the exhaust pipe (opposite side to the valve pipe assembly) looks broken - it's not sealed anymore, but i dont know if it ever was sealed! Being an exhaust, I dont know if it needs to be sealed.

I can see a catch for the exhaust pipe, and note that its got a screw beneath it, but I cant figure out how to remove it to check it.

I think when it's fallen the casing has been knocked somewhere. I think that if I can dismantel the motor mounting and put it back together, it should fix the problem.

Is it possible to remove only the 4 screws that hold the top and bottom of the motor casing together without having to dismantel the rest of the vacuum?

Dyson will charge £60+ for an engineer to look at it. Since I've knocked it over, and presumably damaged at it, I expect it wouldnt be repaired under guarantee.

Is there anything else I could try?

Thanks in advance.

CD