I've heard lower right bolt on the water pump will drain most of the coolant from the engine block. I've only heard that and not tried it. I will find out soon when replacing my water pump.
Lets hear it for Land Rover not giving us a drain **** on the radiator. WTF!

 

If you're thinking about draining the block, why not just use the block drain plugs?

 

All you have to do is remove the lower radiator hose and remove the reservoir cap and you'll be fine. You have to flush it anyway if you're changing coolant types, if not just refill and bleed the system.

 

Good luck on getting to those block drain plugs
They are damn near impossible to reach, just like anything else on a disco.

 

The right side plug, I gave up on, I admit. However, I pulled the left hand plug quite easily when I flushed my coolant a few months ago.

 

Yeah to reach those engine block drain plugs you need Inspector Go Go Gaget Slinky arms and an old school square drive socket with a wobble extension. After asking a few shops in my local area if they ever attempt to remove them. They all said no. Seems like a good thing to leave alone.

 

Just to make sure I didn't imagine the coolant flush process, I checked the scrap engine I have in the garage. The right block plug is directly behind the engine mount, but the left is a few inches in front of the crank sensor. Box end of an 11mm combination wrench. I don't remember if I broke it loose from above or below, but I do remember I re-inserted it in the block from above, by feel.

I am 5'9" and 140lbs, have been working on vehicles for the past 19 years, so possibly have developed the Go Go gadget Slinky Arms

 

Thanks all. Just did the job. As always, it was a royal PITA! Getting the damn hose off took forever. I wanted to break as few other things as possible while fixing this issue, so went easy for a while... then just used brute force after cutting a slit to release it from by the block. She just did not want to come loose. Putting it back on wasn't terrible, although I really hate getting coolant lines back on!
Also, managed not to make a huge mess somehow which was a bonus!