starter motor not disengaging on 300tdi disco

Out in 300tdi 95 disco other day. got burning smell and unusual tinny rattle from engine bay. Pulls over for a look, turns off ignition and engine continues to run and starter motor trying to crank engine???
Several attempts and finally engine stopped.
Car starts great but when that noise is present will not turn off and starter engages in off position with engine still running. Burning smell and smoke from starter motor.
SO, I get a starter motor i know to be good and fit this... Same problem, starts great as always but won,t switch off. Noticed wiggling the key in the off position always turns engine off. significant?
Central locking, which works off key not fob, stopped working as well. Coincidence?
Have looked through old posts, Still am, but would appreciate some advice.

i would say that the problem is the ignition switch.if the ignition is not turning off properly then the fob wont work.