Potterton Programmer not controlling stat?

I developed a fault on my Potterton system as a direct result of trying to change the in room stat (Potterton PRT2) with a new Honeywell DT90e. I wired the new stat incorrectly which blew the 3amp fuse on the fuse spur next to the Potterton EP2002 programmer. Before replacing the fuse with temp 5amp one as I didn’t have a 3amp one in the house – I tried reinstalled the previous stat as it was wired before.

I turned the fuse spur back on and the programmer seems to be working ok, all the lights come on, the program has been saved and the sliders work. However the stat in the room stays permanently on – triggering the Potterton boiler when the temp drops below the desired temp regardless of the setting on the programmer (programmer is switched off and the stat is still kicking the boiler on).

The problem only seems to impact the Central Heating as the programmer is controlling the hot water correctly. I tested this the morning with the stat set to lowest temp (reached light on so the boiler off) then HW set to Timed on the programmer – the boiler kicked in to power the hot water after the shower was running (after using existing hot water in the tank) – I then switched the HW off at the programmer and the boiler switched off.

I suspect I have either rewired something incorrectly or I have blown something on the circuit board – any ideas?

Thanks