Alfie, looks like you followed my advice as per PM. If motor feels "clunky" to rotate I would suggest that a magnet has come loose. Other than stripping down the motor and checking security of all magnets and re-glueing where necessary I would suggest replacing motor.
Speaking to Kevin yesterday he said that the receiver was still being powered and connections appeared good.
Replacement can be found here
www.centuryuk.com/Spares/Aeroplane-Spare...ss-Motor-%28850kv%29
Order early enough in mornings and get next day delivery!