But "You could do it because I know someone else that has done it in some random other council in the UK" is not exactly professional or good advice.Cracking!
However, I’m glad the OP is aware that you can still get Planning even if others have done it along with sub-standard garages.
“Each application is determined on its own merits and is on a case by case basis...” Good old Planning caveats.
If the OP is not sure of his council's policies, and the merits of an application, then it's a massive risk to not only apply and be refused, but to then risk enforcement and having to de-convert it back to a garage and being conditioned to never ever being able to convert it in future.