Welcome to Flyertalk Pumplekin, welcome to the BA board, and thank you for joining up here and letting us hear of your experiences.
OPO is indeed known as a location without confirmed lounge access. I was allowed in, but many other FTers were not. It's also a Priority Pass and cash lounge so there are ways in (and it's a better lounge than LIS or FAO). There is a bit more detail about this, and the lounge-less locations, in the Forum's Dasboard thread for Europe lounges.