euro lock removal?

I am replacing 6 euro locks with anti bump/snap locks.
I have done four locks with no problem. But locks 5 and 6 are causing me major problems. Both are on UPVC double doors with lockmaster multi-point lock and yale euro locks. Both euro locks did NOT have the normal securing screw. But no matter how I try I can't get the euro locks out. They are loose and are moving backwards and forwrds by 5-7 mm. But no matter where I position the key they won't come out. Having already done four locks I no how they should come out. Is there some other hidden screw holding them in.
I badly need help - I now have 4 doors with good locks and two with std. euro locks. Please someone help me.