Balisongs are illegal in the UK (foolish of you to admit having them) but not dangerous cargo - their carriage won't jeopardise the safety of an aircraft. Carrying flammable stuff in your suitcase is potentially dangerous and being smug and cavalier about the fact that you didn't get caught is unhelpful at best.
You've probably gathered that I work for an airline and after a cursory glance at the regulations I didn't see a specific mention of Hexamine (although it does have a UN number and appears in the ICAO Dangerous Goods Response Guide so thus has a response drill). For example, you aren't allowed to carry matches in your luggage but they're OK on your person (because if they catch fire, you'll know about it).