If you are without status, but in CW then you have a choice of T5A North, T5A South and T5B for a lounge.

If your flight is CW then it is more likely (but not certain) that your flight will depart from T5B or T5C.

If this applies, then your best bet is the T5B Lounge since it is generally quieter and would end up being nearer to your gate.