The Firefly, while somewhat ponderous in the roll, is a good instruction aircraft with inverted system and nice controls. It also has excellent visibility.
Doing aerobatics with the letterbox view out of a 152 is not ideal: not that comfortable, harder to keep a good lookout, and you want to develop where you look to stay ahead of the aircraft.
The Decathlon is a good trainer and more capable than the Firefly, but very few in the UK.