Update on UK passport application. Just got notification from VFS in Bangkok that my childs first passport has been delivered to them and awaits collection. From being sent to the UK processing and returning 23 days, so not too bad. The UK passport office is now on strike for a month so big delays now possible.
TLDR : Answer Summary
A user updates about their child's UK passport application, which has been processed in 23 days despite ongoing strikes at the UK passport office. Comments discuss potential delays, the ability to travel internationally with an old passport that has not been officially marked, and inquiries about obtaining a UK visitor's visa for a Thai spouse.