Don’t forget that all BA Galleries/Terraces lounges offer champagne on request; often the same stuff they are serving in the F lounges.
Congrats on your recent “gilding”.
Your Gold Card entitles you to use the Arrivals Lounge in T5, regardless of what class you are travelling in, so pop in there (if it’s still open) and enjoy a full English, the morning’s newspapers, a quick massage at the Elemis Spa and one of the special gurgling showers.
If you have acres of time on landing, ask for one of the “infinity baths”, so called because they take an infinity – well 45 minutes – to fill up. Usually preference is given to those travelling F, but it’s really no great benefit!