Sprained ankle

It was definitely an inversion, and I'm sure I heard something pop. it was really painful for a minute or two, then subsided, but started swelling up straight away mainly on the anterio-lateral aspect of the ankle, but later the swelling spread to my foot.

Helda. This sounds like you have torn the ligament, but to what extent i can only guess. As its ligament, it has poor blood supply, nerve supply and as i'm sure you know - serves as a bone to bone attachment. Hence why it was painful for only a minute or two, then subsided. It has no muscle attachment so it now means that your joint is now "lax" as it has no ligament to keep the talus and fibular together (does that make sense?).
The swelling to the foot is merely blood following the laws of gravity and pooling into the foot - hence why elevation will help to remove the pooling.
Can you get a look over at hospital? Ligament tears can be complicated, so its always better to check.
Just gonna PM you my number.