I booked my first ever BA holiday a few months ago. The experience has been a nightmare both in terms of financial mess (mistakenly charged full amount when I used GUF to upgrade flights, had to fight to get it back) and handling of rebooking when BA cancelled one of the flights which was both extremely slow and extremely unhelpful. Worth noting that GGL won’t be able to touch a ba holiday booking so you’ll deal with ba holiday office (in Bremen in my case). They are totally useless.