Oscillation on opamp output with P-mosfet
It's a common problem when trying to design a constant current source using a MOSFET as the output device and is usually fixed by increasing the value of C15 from 1 nF to something higher (maybe 10 nF): -

The problem is caused by the extra pole introduced when driving the MOSFET gate-source capacitance. The extra phase shift introduced by the MOSFET gate-source capacitance and the output resistance of T2 (emitter follower) is enough to degrade the phase margin of the op-amp to the point where it naturally oscillates when feedback is applied via R2 (the input resistor to the op-amp.