Totally not your bad. In the first post, I did write "I did measure voltages at the programmer and boiler ends but the results didn't help my understanding." and I should have expanded on that because I did not measure 240v across any of the terminals.
So. Is this what we have:
240v supply live from isolation switch to L on new prog room stat
240v supply neutral from isolation switch to N on new prog room stat
Black (sleeved red) conductor on the white flex to 4 on new prog room stat
Remove link wire between L and terminal 2 (common)
If I have that correct (and I think I don't) then, on the white flex we have blue and brown conductors which are now unused (but have voltage on them) and would be capped-off.
So. Is this what we have:
240v supply live from isolation switch to L on new prog room stat
240v supply neutral from isolation switch to N on new prog room stat
Black (sleeved red) conductor on the white flex to 4 on new prog room stat
Remove link wire between L and terminal 2 (common)
If I have that correct (and I think I don't) then, on the white flex we have blue and brown conductors which are now unused (but have voltage on them) and would be capped-off.