I'm currently travelling in Europe on an Australian Passport. I also hold a Korean passport.
I'm trying to decide whether to overstay and looking at my options. Having trawled through the threads there seems to be a lot of differing opinions about this....
I'm wondering if it's possible to go to the UK using my Korean passport (even though I arrived in EU using my Australian passport) and then re-enter EU with my Korean passport...therefore getting another 90 days on the Korean passport? Is that legal or possible?
My other option is to overstay (probably need another 5 or 6 weeks over the 90 day period) but am naturally nervous of the consequences.
Any suggestions much appreciated.
NO, not legal, not possible. You have to exit with the passport you entered.
Before you ask: yes, you could try to re-enter immediately on your Korean passport, after having left Schengen for the UK. This might work (I'm not sure how well UK border patrol and Schengen border countries exchange information), but it's certainly not legal.
There is really is nothing further to add to what bentivogli has already advised you on.
Just to reiterate, it's illegal and the authorities will, for sure - give you a very hard time after they've checked your movements and paperwork.
It would be interesting to know in what country you plan to overstay. Depending on where you are there might be alternative options.