I'm a bit confused cos here is the Discovery sport section and your title is 2000 Disco so is it a Disco 2 made in 2000 or some Sport with the 2000 prefix?...if it's Disco 2 most probably the SLABS ECU is draining the battery cos it doesnt "go to sleep" as it should after max 1.5 hour the ignition is off which can be a ECU missbehaviour or one of the door switches is not working well and the system "thinks" a door is open and doesnt go to sleep... i'll tell you more if you confirm it's a D2 and if it has or not air suspension
My friends call me Fery
2000 Discovery Td5 ES manual
Hawkeye v.6, Nanocom EVO,
VDM UCANDAS, oscilloscope
if you think my english is peculiar it means you didnt hear my japanese
ALL MY ADVICES ARE BASED ON MY OWN KNOWLEDGE AND MY WAY OF UNDERSTANDING THE DESCRIPTION AND OPERATION OF SYSTEMS... I'M NOT A LAND ROVER TRAINED SPECIALIST JUST AN ADDICTED ENTHUSIAST.