"..and can just find my way to the BA lounge for the duration."

Sorry NM, the BA lounge is the actually AY lounge - one on either side of the immigration counter. At least they have a nice view over the runway and gates. No showers. Even the check-in staff are wearing AY uniforms and are amused when you ask "where is the BA check-in counter".. No BA OLCI option for HEL either. At least the seriously unhumorous immigration people will stamp your passport exactly where you ask them to stamp it. ATMs are called OTTO - same brand as our wheelie bins but different shape.