When I was there in October I heard the staff saying preflight dining was only for club/1st pax not for status pax in wt(+).

They gave me a dining voucher/ invite on entry but weren't too hot on checking before access to the club buffet so you could have easily eaten without the invite.

I was in club, I think it is also shared as the first lounge but first has a separate dining area with waiter service rather than buffet.

Overal it is pretty nice - like a mini galleries club lhr. Food good as well - hot and fresh.