I wouldn't listen to the naysayers (I am one of them though!).
If it is your first time I would use the CCR. If going through T5 don't forget to use the First Class checkin to the far right - it ensures you walk straight into the First lounge. I wouldn't stay there - it is usually packed with business travellers and the food is limited even if you order and don't get the buffet.
Exit left and walk straight into CCR. Get a dining table in one of those stupid enclosed booths and order food and drinks. If it is your first time - it is nice and fun and relaxing. Make the most of it.
I wouldn't bother with wasting your time trying other things.