[FERNSEH]

I think it is agreed that employing the 10 volt battery as the supply regulator is not all that good really.
The attachment shows the circuit of the supply regulator of the Ekco T544 portable TV of 1972. If the mains transformer can supply sufficient headroom voltage I'd consider using this power regulator in the TT1.
The Ekco T544 draws much less current than the Pye, 1.25amp as against at least 2amps in the Pye so the OC26 or AD149 series regulator will have to be shunted with a 10 ohm resistor. The series regulator transistor in the BRC 1590 uses similar an arrangement in order not to exceed the current limits of the AD149 transistor.

Two AU113 line output transistors have been ordered from an online supplier in Holland.

DFWB.