Hello Matt,
This concerns, since any oil which has been in the sump of a diesel engine - for even the shortest of time - will be black. So ‘clear’ will certainly ring alarm bells.
Appreciating everyone has to start DIY mechanics somewhere, and I don’t want to make this too critical, but since you are asking if the sump plug is the same as the drain plug, it really does demonstrate that you are on A of the mechanic’s alphabet, and that’s fine, but I think you would be well advised to have someone by your side who has a bit more experience, and can guide you through.
Now, clear oil might be expected from the gearbox ( if it has a drain plug) and one begins to wonder whether you have indeed removed a wrong plug. Having said that, 200/300mls would be a small quantity to run out of there, whatever angle the car is at, but to run out of the engine sump of a diesel engine just seems to ring alarm bells to me.
Photos of what you’ve done Matt, so we can try to help?
Kind regards,
Gareth.