The mainline platform forecourt at Liverpool Street Station is very open and airy. The trains as far as I am aware do not go through tunnels to go out of the station, although there may be a few short bursts of tunnels for a few seconds here and there in the first few miles (under bridges etc). Here is an architectural mini-guide showing some pictures for you to see the forecourt. If you are really concerned call the station helpline and ask their advice.



