Thanks for the additional info Charlie. Yes I'm running at 5v and each sensor is on it's own pin on the PIC.

The controller was installed at the weekend. It sits on a stack of three vivariums, with the fouth being a large 160cm x 50cm x 50xm the other side of the room. The cabling for heater, light and two sensors are routed in trunking over the door and along the skirting board to the unit



I've updated the schematic and PCB drawings to use 4K7 resistors... Where I got 10K value from I don't know !