Yes the intention would be to switch 240v AC either through SSR's or zero crossing driven triacs.
Won't work very well, if at all, with "high frequency" PWM. For "dimming" AC you would need to create a phase angle control.

So If I follow your drift, a PID routine would still be required, but rather than a low frequency pulse, the filter is used to determin the pulse width in a high requency PWM ?
First part yes, second part no.
Using proportional control only will most likely give you the result I explained in my previous post. You will need at least PI.
As before, you can not use a normal SSR to power a AC device and simply feed a "high frequency" PWM signal to it to "dim" it, it's not like dimming a LED with PWM. You need either a voltage controlled phase angle controller and drive that with a voltage created by low pass filtering the PWM output. Or you create a LOW frequency PWM signal with a period in the seconds range (which I believe is exactly what I beleive Darrel created for you in the version you have already) - and it's like that for a reason.

If you where to rectify and filter the incomming AC you COULD then use a high voltage MOSFET or IGBT to PWM the load but, well....

/Henrik.