im looking to fit an oil pressure gauge but not sure how, where does the oil pressure sensor live on a td5 defender, do i use a sandwich plate although i can't think there'll be room on the filter, so the supplier was talking about T-ing off the original sender, is the original sender electrical or mechanical

The sensor is down near the oil filters, a 2 wire plug but only one wire does anything.

Its screwed into the oil cooler facing back towards the bulkhead. If you dont know the oil cooler is bolted to the turbo side of the engine below the exhaust manifold. Be careful when you unscrew the sensor as they can seize into the cooler and the alloy cooler housing can crack. On my 10p engine cooler there was a blanked off oil gallery fitted with a removable threaded plug where LR intended to fit a pressure gauge. However on my later 15p engine it does not seem to be there and just has a blank casting instead of a threaded plug.

cheers lads i'll look tomorrow, mine's a 10p so hopefully will have the blanking plug that i can remove and use for new sender

Pressure sensor faces towards bulkhead and is screwed into oil cooler roughly marked by the red circle. You will need to remove the turbo heat shield to get at it unless you have super bendy hands and tools.