It's an L29 Delphin, although the tail section has been crudely removed from the top of the fin and attached at the base, don't know why.
The Galeb had much less sweep back on the fin, and lacks the circular access panel just below the roundal.
Without going into the subtleties as the differences in the fillet and spine on the top of the fuselage, the two small intakes on the side of the fuselage and the aerial on the top, the design of the canopies suggests it's a Delphin. The rear canopy of the Delphin slid back, and this feature can be clearly seen, although the Perspex is long gone. Also, the Galeb had panels inbetween the two cockpits, F4 style. The Delphin's design was a more simple Hawk style.
I don't thing the RoAF ever operated Galebs, although when I was there in '99 they had an awful lot of Delphins in a paint scheme similar to the one in these photos. The Air Force was so strapped for cash, the condition was similar too!