PCBs are available for a somewhat modified version of the soft-start project. Rather than the MOSFET switch, the PCB version uses a cheap opamp, and provides power and soft start switching. Full details are available when you purchase the PCB, but the schematic and a brief description is shown below.
The delay time for all circuits shown has been revised. The optimum is around 100ms - sufficient for around 5 full cycles at 50Hz, or 6 cycles at 60Hz. It is also quite alright to run the transformer to around 200-500% of full load current at start-up, and the formulae have been revised for up to 200%. Without the soft-start, inrush current can be so high as to be limited only by wiring resistance - well in excess of 50A is not at all uncommon for average sized 230V transformers.
The main timing resistor (R1) may need to be varied to get the required delay. MOSFETs have a wide variation of gate threshold voltage, and the timing will need to be adjusted to suit the MOSFET you have in your circuit.