Now the Catalans host the Scots in Round 2, while the Irish giants welcome the English outfit to Thomond Park, with all four sides knowing the table could be even tighter come Sunday afternoon.
"This group is going to go right down to the wire," said Hook, who previously played Heineken Cup rugby with the Ospreys.
"It's a tough group that's going to be wide open, as we've seen from the first round of games with the two home teams winning.
"You have to win your home games. If you don't win away from home, the next best thing is a bonus point and we got that against Gloucester, which was very important.
"The Heineken Cup can bring out the best and the worst in teams so the Edinburgh game is huge for us and we will have to be right on the money.
"If we take the performance against Gloucester into Edinburgh with the crowd we've got there we should be okay, but we can't rest on our laurels at all. If we think we can just turn up and win then we will come unstuck - we need to back the performance up with a win."
Perpignan did everything but win at Kingsholm last week as they threatened to take early control of the pool after a two-year absence from Europe's premier club competition.
Only a late, late Jonny May try robbed Marc Delpoux's men of a famous away success after Hook had scored all 22 points for the visitors courtesy of a rare full house of a try, conversion, drop goal and four penalties in the West Country.
"I was obviously happy with my performance but it was just so frustrating at the end," added Hook.
"I was happy with our first-half performance, but when the rain came down the game tightened up a bit. But I got the ball in space a few times and managed to find some room.
"We were holding on in the final 10 minutes but we could have buried the game in the second half: we had opportunities to score which probably would have sealed the game and, away from home, you can't let teams back into the game. Every game is big in the Heineken Cup and we are always targeting wins but obviously it's more difficult away from home.
"There are a lot of positives to take from the game but plenty to work on as well. We fronted up well and now we've got to back that up against Edinburgh at home."