Yes, you can go from T2 to holiday in a T1 location, but living in T2 means you have to follow the T2 rules whilst in a T1 location. So you can't go to a T1 location and go to a pub/restaurant with people from another household.
I'm in T2 London and we're going to a cottage in Kent for a few days over half term. We were going to take a niece and/or a nephew but we can't mix households now so it's just the 3 of us from our household going. We can still go out to the pub or a restaurant whilst we are there but we can't mix with another household (not a problem as we're not going there to meet anyone, it's a holiday for us.)
The advice is not to travel in or out of T3 areas.