hotpoint tdc32 condenser dryer - nasty noise from rear?

4yr old machine, recently started to make a horrible vibrating/grinding noise, emitted from the rear of the unit.
Removed the 3 rear panels and switched on as part of investigation, the machine operated fine - no nasty noise.
refitted the 3 panels, machine is noisy again!
There is a plastic fan type thing that is covered by the largest of the 3 removable panels. This fan looks a bit warped, but i'm sure its notfouling the removable cover.
Anyone had similar experience, and know of a quick fix?