another lounge question - BA/BMI domestic at LHR T1

So, having already requalified for AU next year, I'm now wondering if it's time to tactically do a couple of long hauls with the dark side to get me up to BA AG and gain a few extra benefits from that.
Realistically the lounge I'd end up benefitting from most often would be on my Belfast runs with BMI, so the LHR T1 domestic one. Anyone got any views on how good/bad it is versus (say) some porridge and a coffe from Pret, which was my option today? For that matter, does AG get you access to the lounge at Belfast City? Been delayed there a few times and the one bar is usually packed out...
Thanks
RC
Realistically the lounge I'd end up benefitting from most often would be on my Belfast runs with BMI, so the LHR T1 domestic one. Anyone got any views on how good/bad it is versus (say) some porridge and a coffe from Pret, which was my option today? For that matter, does AG get you access to the lounge at Belfast City? Been delayed there a few times and the one bar is usually packed out...
Thanks
RC