Except LGW, bases with best benefits have internal waiting lists which can be quite long.
As a DEC you will probably be offered OPO, LIS, BCN, AMS, LGW or NAP.
There is a base freeze for DECs and it is my understanding that unions want to introduce a seniority element into the base transfers in the future, so expect to be based for quite a long time in one of the. bases mentioned above.