Two points puzzling me:
-) the controller not having stated whether his "not below 450ft" was AGL or AMSL, how was the pilot to know?
-) some responses see a difference between "going around" and "going around immediately" , a difference I fail to imagine. Surely, if told on final to "go around", one makes sure not to descend any further, then adjusts configuration (flaps, power...) then climbs to circuit altitude or as appropriate, and at any rate flies the circuit as published - i.e. continue straight over the runway until turning into crosswind leg?