I was flying LHR-HEL-BKK on AY with onward flight on separate PG ticket to PNH. Up to one year ago, AY would check my bag through to PNH as AY code share with PG. They have stopped doing that so I arrived at LHR with my two cabin bags, as allowed in J class. The officious young lady at check-in insisted on weighing my bags. I had not realised there was a J-class overall limit of 10kg!!
She tried to tell me it was a health and safety issue so I pointed out that cannot be the case or BA would not allow a combined weight of 46kg in J-class. And I was flying in the A350 out of LHR so space was hardly an issue (I was well within the dimension limits in any case).
I could see the other check-in staff giving her sidelong ... glances.
I guess the solution is to do OLCI, assuming that is an option at LHR. In any case avoid this particular lady (young, Caucasian, English accent).
I had a two hour layover in BKK and thought I might just make the connection but the HEL-BKK flight departed one hour late and I missed the connection by 10 minutes. Cost me a one night stay in BKK and a new ticket to PNH.
BTW, before someone asks, yes it is possible to buy a J-class through ticket to PNH but the additional cost is substantial.