Thank you chaps for looking int this and apologies for creating such a nightmare model.

I actually built it a couple of months ago but I dont recall that I did any wild scaling (although I guess its possible I 'could' have changed the modelling units mid build and done something but I cant confirm)

TBH I'm not that interested in finishing this model as it was just a little concept test but mainly interested in the technique that you use to fix it. (I hope it didn't eat too much of anyone's time.)

Now I know that I will need to look at untrim/trim in future. (Join/separate is normally my goto fixing method). Thanks Micheal for the solution!!

A big thank you to everyone who took the time to look at this.

Simon