I might put a resistor of 470R in series with the emitter of the BC557. It probably isn't necessary, but it would be more predictable over temperature extremes.
I would also put a 10k from the base of the last BC547 to its emitter. Again, just for stability.
Instead of using millions of transistors, resistors and diodes you could use two LM3915 bar graph driver ICs.
An LM3915 has 10 comparators and LED drivers inside so transistors and diodes are not needed. The LED drivers have adjustable current regulation so the LEDs do not need current-limiting resistors.