Disco 2 V8 electronics compatibility with TD5 dash guages...

Hello team - I'm UK based and need some advice for my 110 Defender...its a bit of an unusual one - it has a D2 4 ltr V8 Thor engine fitted plus auto box along with all the D2 V8 electronics including the ECU and BCU. My temperature gauge reads "normal" as soon as you switch the ignition on and irrespective of engine temperature sits at the "normal" level throughout. It jumps to normal as soon as you turn on the ignition which suggests its got power and a signal from the ECU (or somewhere). I've plugged a Hawkeye into the truck and the ECU seems to be getting live / accurate coolant temperature readings from the engine which suggests the problem lies between the gauge on the dash and the feed from the ECU...but I also have no idea if a Defender dash temperature gauge is compatible with D2 electronic feeds...so that's my question - will a D2 ECU send correct coolant readings to a Defender temperature gauge on the dash or are the two incompatible? If they are compatible, and if the temperature at the ECU is reading correctly, what should I be looking at on the basis there seems to be power going to the gauge? Cheers.