My Family Member permit was approved - Civil Union Partnership with separate Surnames. Can I join my partner at the EU Customs queue when entering the UK?
No, but they can join you in your queue. EU passports can go through digital scanners, so when entering countries like the UK for example, the EU queue is to machines only, if your passport was from a different country and was not eligible to use in the machines then they would not open to let you through.
I have gone through non EU passport lines with friends before so we didn't get separated, and boarder control are fine with that, but it would not have worked the other way around.