replace bulb

Hi Does anyone know how I get the black plastic bulb holder out of a light without breaking it? It seems alot harder than it ought to be as its loose and doesnt appear to be attached to anything within the casing.

How do I replace the light bulb in below bathroom light fittings, metal ring seems sealed/plastered to roof , no give in the inner circle of frosted glass either. normally these are spring loaded to the plasterboard but in my case they seem fixed/bonded to ceiling. Is this just poor...