Originally Posted by LondonElite

Whilst that thread discussed a different situation, and although the transit rules are different (usually, but not always, lighter), I believe the point still stands. That is that the people who are the gatekeepers to boarding the aircraft are not highly-trained immigration agents, with access to significant resources and supervisors who generally know what's going on. They are contract staff with a cheat-sheet who can deal effectively with 85% of situations, 95% of the time. I have no data to back this up, but my hypothesis is that they are responsible for more false negatives than positives (in other words, they'll err on the side of caution; probably the result of their training). They will sometimes rely on information sites such as Timatic (which is the breast that all FT, wrongly, since it too publishes mistakes, seems to suckle at).

My point is that you are unlikely to get the best definitive answer here. I believe the answer to your question is no, you don't need a visa, but I would check, for example, the published UK and Indonesian government sites, and possibly enquire at the consular office of the Indonesian embassy wherever you happen to be at the moment.