Thanks for the responses. Granted it's not an everyday occurance as evidenced by the fact that posters here on the forum haven't any first hand experience; and this is where I may come unstuck. The lounge agent on the day may not have come across this situation either. Not the end of the world by any means but access would make the long-ish connection more bearable to what I expect will be a weary traveller.

@yellow_peril My understanding is that it is the higher class ticket that determines the lounge access on an itinerary. So, in your case you will have access even on separate tickets.