How can I fix My White Knight 767c Tumble drier?

The motor on my White Knight 767c Tumble drier has become excessively noisy. I cannot seem to get at the motor. I have removed all screws necessary, But don't seem to be able to remove the ?impeller? to remove the back plate from the carcase. I get that the centre bolt on the impeller has an opposite thread? but can't seem to remove the blighter. I have found the three screws which support the drum, I know I will have to remove them to remove the back, Oh yes and I have disconnected the power :-) Can anyone help please?