You'll be lucky to 25V out of this thing, at full load. Q4 & Q2 drop a total of around 2V and the output stage of U2 drops around 3V.
That's the least of the issues. The TL082 is only rated to a maximum total supply voltage of 36V, yet this circuit gives it 38V or more, especially at light loads, when the voltage on the transformer will be higher than the rated value. I Googled the data sheet for a 300VA toroidal transformer.
The first hit states a regulation factor of 7.1%, so that's an open circuit voltage of 24×1.071 = 25.7V, giving 25.7×root(2) - 1.2V = 35V on C1, now note that pin 4 is connected to a negative voltage doubler and a 5V zener diode, giving -5V, making the total supply voltage 40V. This is assuming the mains voltage isn't also on the high side.
One fix is to use a lower voltage transformer, a lower voltage negative power supply and an op-amp rated to 44V, but that won't get rid of the issue with ripple on the output, when the voltage setting and current drawn is high.