Okay, this article solves the mystery of that Sunday night with both the Empire awards and the Olivier awards. They were at the same LOCATION--just different rooms! (I thought they were going to be held a day apart, but that must have been a mis-print.) Here's the link, and a few quotes.

http://news.google.com/news?q=james+mcavoy&ie=UTF-8&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&sa=N&tab=wn

Winners for this year's 32nd annual Laurence Olivier Awards, London's equivalent of the Tonys and the UK's most prestigious stage awards, were announced last night at a star-studded ceremony held at the Grosvenor House, Park Lane. With the Empire Film Awards also taking place at Grosvenor House on Sunday night, there was a real abundance of stars on the hotel's red carpet for arrivals...

More happily for James McAvoy, the doubling up of ceremonies meant that he could pick up his Empire Best Actor trophy for Atonement and then nip into the ballroom, Empire goodie bag in tow, to support his wife Anne Marie-Duff, who was Olivier-nominated for Saint Joan (though she lost out to Kristin Scott Thomas). He did seem to have a little trouble finding Duff's table in the dimly lit ballroom, arriving after the ceremony began.....

The Football Factory star Danny Dyer... was another Olivier presenter this year... Dyer recently caused headlines when he launched a blistering attack on fellow British actors Orlando Bloom and James McAvoy. Rather than talent, said Dyer, they owe their success to, in Bloom's case, a good name, and in McAvoy's, to a "a floppy hairdo" and "period dramas".

Did McAvoy get his own back on the night? If so, there were no witnesses. However, the similarly coiffed Dan Stevens, ...took the opportunity for a swipe when he announced the award for Best Set Design. He confessed to still having some "issues" to deal with concerning his own "floppy hair, which I wore tonight specially for Danny Dyer".

The whole awards night was literally overshadowed by severe weather warnings which predicted 80-mile-an-hour winds and advised Londoners to stay at home at all costs. Luckily, the Olivier guests were undeterred, battling hail and rain to attend the 2008 ceremony.