Re: Henry III & Edward I's Drooping Eyelid
Well, portraits of people before the late 15th-century are very scetchy sources when it comes to looks. I believe that (altough I cannot vierify the source with 100% certainty) Henry VII were among the first persons to have his portrait actually look like him, and he ruled between 1485 and 1509.
The important thing about statues, paintings and the like were not that they correctly represented the persons actual looks, but rather the fact that only powerful people had paintings and sculptures of themselves, and thus manifested their own prestige.
For example, you can compare a painting of Edward the First with the stone-figure of him in York Cathedral (which happens to be my Avatar at the moment). They probably look nothing alike one another.
However - to answer your original question, I couldn't tell you really. I am an enthusiast when it comes to Edward the First in particular so I'm rather ashamed of not knowing the answer to this one. The litterature I own does not specify which one.
But, if your litterature says that it was the left eyelid, then it probably is. As previously stated, portraits of people before the 16th-century are not very trustworthy, not that the later ones are perfect either, but still...