Hey there!
I have been bothered with this question for some time. I am holding a Master’s Degree in Finance from a good University, having studied in Spain, Germany and the UK, worked for some good well-known banks in Luxembourg and Germany but could not kick start my career until yet. (Well, salary is good... but nothing extraordinary ;-) )
So, I am wondering if I should apply for some good Business Schools in the UK or France... and doing an MBA. Is 30 too old? I don't think that i will get a job in Consultancy or IB with 30 + afterwards… And if I "invest" 40 k to 70 k Euros... I am not sure if I will get a positive NPV...

Of course you will. 30 is the average age on most top European MBA, and you can double your salary.

Yes, look at these schools:

LBS: average age 28.6
INSEAD: average age 29
HEC Paris: average age 30

Your quant background and international experience in banking will look good to IBs.