What did I do wrong here?
Nothing at all Glasswasher, if you're not happy with your approach then go around and have another go.
The fact that you made the decision to go around twice because you were not happy to continue shows that you are not prepared to take unnecessary risks and have the presence and maturity to make the correct choice.
I did one recently, a go around that is, for the same reason, an aeroplane still on the runway, and I've got over 18,000 hours and fly B767s. It still happens from time to time.
Of course I had to explain to the passengers what was going on but all you need to say to the tower is exactly what you posted. An aeroplane was still on the runway and you weren't happy to continue.
Good luck with the rest of your training.
Regards,
BH.