Brake problem

Had a single circuit master cylinder replaced with a dual circuit a couple of weeks ago since then I've been using a shit load of fuel , have'nt been using the car much till the last couple of days and today I noticed that the back brakes are binding when they got warm--actualy warm is a freekin understatement (this probly explains the fuel) so I backed off what seemed to be the worst and adjusted the handbrake just in case and went for a short run - by the time I got back-the pedal has gone as hard as rock (like when the handbrakes on and you depress the foot pedal) and the brakes are binding again--not quite as badly as previously but far more than they should be .
I have'nt got a clue what is going on with these brakes as I've never come across this scenario before and as usual the manuals I have ---well the less said the better.
Can anyone help with this one ?????

make sure there is around 1mm free-play between the pushrod (at the pedal) and the master cylinder...?

yes sounds like no freeplay in the pedal as per above

Adjust this then bleed the brakes then adjust the brake shoes then the hand brake last

It maybe that you do not have a compensating valve fitted in the rear brake line mine has duel master cylinder.

Trevor//

Thanks Fellas that was it--pushrod--someone had omited to pinch up the locking nut 🤪 which was siezed on the adjuster shaft (praps why)------it's interesting-- freeing one of these off-- in the car---🤖
Cheers, Al .