Bit of an update.
Done everything that roger said and running of battery alone it lasted for over 20 mins. Smell was still present.
So connnected it back up and got annoyed so kept the thing running when the smell got stronger and held it on 2k. After a minute or so the smell started to clear and eventually went.
So went for a drive with lights on heaters on the lot and the smell has not come back. Only thing I can put it down to is paint on the pulley or shaft and just needed to burn off.
Will keep an eye and nose out for anything over the next few days.