Lounge access depends on your outbound flight (DXB-LHR in this case). As an economy passenger you are not entitled to lounge access, however as a Gold member you can use either the business class lounge in T1 or the Skywards lounge in T3.

T1 lounge is a lot further away and has less food selection but can be quieter as it is mostly Silver members only but. T3 lounge is the new biz lounge and is much larger with better facilities...