Rich,
See CAP413 Chapter 4 para 1.10.
If the controller had required you to go around immediately he/she would have used "G-CD Go around I say again go around. Acknowledge".
With the phraseology that was used the only requirement was that when you went around you did so not below 450ft therefore what you did was perfectly acceptable. On the other hand had you wished to continue the approach for practice you were free to do so provided that when you did go around you did not descend below 450ft.