Presumably you've had an assistant press the brake pedal gradually whilst you 'feel' the braking effort at each wheel, (car raised wheels off couple of wheelbolts in and long lever to apply wheel turning effort via those bolts), check handbrake too like this.

Assuming that there is the sort of braking effort you are expecting at all 4 corners, i'd be inclined to strip the pads from the front brakes and make sure the pistons are free in their pots, and that the sliders are moving freely and lubricated adequately, obviously have a good look at the pads and if any doubt replace them, cheap as chips anyway.

Seeing as you've applied heat to the calipers might be an idea once all done to really stand on the brakes as much pressure as you can reasonably apply, any weaknesses you want to find now not out on the road, any doubt at all in your mind fit new front calipers.

You may have the handbrake cable over-tight, thus preventing the self adjusters from doing their job. Try putting lots of slack in the handbrake cable, driving around a bit and applying the footbrake heavily.

I also agree with gb about having an assistant and feeling the braking effect at each corner, although an MOT testing station with brake testing rollers may let you measure the efficiency at each wheel more accurately for a small fee.

Many years ago, i had a battle to bleed the front brakes satisfactorily, on a Mini 1275GT. After much trying, the solution turned out to be removing the front pads. Then, using a couple of tyre levers as stops, the pistons were pumped out until touching them. The brakes were bled as normal, and after putting the pads back, the pedal was A1. For some reason, the air would not purge with the pistons right in. Maybe this may help you.

No ABS. The drums were tricky to get off because the flange on the stub axle gets caught behind the brake lever, so although it was loose it took a while to wriggle it off. Guess it would have helped to release the HB cable inside the car first. After re-assembling, the handbrake did come right up and I had to adjust it back. Maybe I'll try slacking it off and pressing the pedal and then setting it again. I haven't taken off the shoes and springs yet so I guess I will try that to see how the adjusters work.

Thanks for the advice so far, Mike