Neither who you buy from nor whether it is a single or multiple PNRs is relevant for lounge access purposes.

however it’s great that you booked as a single pnr because that’s a relatively tight connection given the t4 departure and even more if you have luggage: you’ll be protected throughout and have any luggage through checked. this would have been a very unreasonable flight to book as two separate tickets whilst as you have you can relax and know they will sort you out if there is any issue.