I have asked Harold and he also said that BMW don't sell them
But he did also say he's never heard of anyone breaking any in a 135i before.
I do trust the shop, he's just said that in alot of Porsches they don't come out very easily and quite often need replacing (he builds alot of porsche race cars)
I'll confirm that they have the right tools to do the job and just get it done, just worried me a little when they said that it is a possibility