I believe The Big Breakfast was live on Christmas Day 1992, but all subsequent years were pre-records.
The following two years saw Christmas Day fall on a weekend, but there was certainly a special shown on Christmas Day 1994, "The Big Christmas Breakfast" which was an hour long pre-record shown in the afternoon rather than morning. I think I have it on VHS somewhere, hosted by Paul, Mark and Gaby - it was the first time the standby blooper reel was shown, which resurfaced on The Biggest Breakfast Ever.
As mentioned, that was actually at 9.25 - and was the only time Paul and Mark presented together. At 5.30 that afternoon, though, they showed Zig and Zag Entertainment Cops, which I really enjoyed (but the series eighteen months later was rubbish, they'd lost it by then). There was also an hour long show on Christmas Eve 1995, dunno why.
For the first Christmas it was live every weekday from 7-9 as usual, including Christmas Day, and then there were three live shows in just over 24 hours with programmes on New Year's Eve and New Year's Day, plus the the New Year's Eve show at 11.30pm of course. The New Year's Day show was definitely live, too, I remember watching it, and they played the first ever Spot The Sausage during it.
In 1993, there were the first pre-records the week after Christmas (but not on Christmas Day which was a Saturday). Those days the first hour was Zig and Zag linking cartoons and the second hour was mostly clips with a few games and features between them, I remember some old Families of the Week coming in and the crew doing Dish The Dirt. I really loved those shows actually, but the show was at the height of its powers in those days.
I lost interest completely in later years but I remember in 1996 the pre-records ran 9-10, cos the show was dying on its arse at the time.