I think I'd be really pissed if someone did that to my 406
I think that probably won't have any effect on the structure of the car (not that I have any experience or qualifications in this area). You could maybe push it out by drilling through the floor pan -but- as you say, it'll be messy. The proper way would be to cut it off, straighten it, and weld it back on (hideously costly and messy too). It'll also depend if the garage is admiring fault, if they're paying then the ball's in your court.
Other than that, I'd be concerned with the damage to rust-proofing, it won't effect integrate how it is but add a little rust...
Talking bollocks sin©e 2007
2004 D9 2.0 HDi 110 Estate lhd VF38ERHZF81657352 - now slod
1991 Yamaha TDM850
2008 Toyota Recall4 2.0 VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVTI ATM LHD JTMBH31V90D007261 - flimsy piece of crap.
1953 Matchless G3LS - Seriously!