The victory prevented second-placed Villa from overtaking Blackburn Rovers at the top of the Division 2 table.
Hornby-Forbes (pictured) gave the Seagulls a 61st-minute lead, while his replacement Tilley added the second six minutes later.
Bjordal completed the scoring in the fifth minute of stoppage time to leave Brighton two points off the play-off zone in sixth.
The Seagulls also have a match in hand over fifth-placed Fulham.
Brighton: 9 Feb v Hull (A) PL Cup
Aston Villa: 12 Feb v Ipswich (H) PL Cup