we are arriving into Terminal 2 on the 28th Dec and want to go to the business lounge in terminal 1 before getting a flight from terminal 3 eight hours later. We just want to know if we can go between the bu
So it appears there is a means to get between the terminals if you're a transiting passenger, but you have to take the bus, not walk.
You should not have any issues traveling between Terminal 1 and 3. As you are arriving at Terminal 2 and have a connecting flight from Terminal 3 you will be put on the transit bus to take you to Terminal 3.
I would like to add a point to @Mark's answer that unless you have a boarding pass for Terminal 3 or 1 (gates A, B or C) you cannot freely move between Terminal 2 and Terminal 1. The airline has to specifically allow you to go there, because you may need to use public transport and they will ask to see your boarding pass before letting you on the bus.
Terminal 1 and 3 are connected, so you can freely walk around; and to get to gates A (the dedicated A380 gates), you need to take the train.