It's really quite simple. Basically two rules:
- No individual product over 100ml capacity
- All products must fit into a single clear bag (20x20cm) per person
More info here:
https://www.heathrow.com/at-the-airp...ge-and-liquids
If you follow those rules you shouldn't have any problems as all. There is no need to throw away your chapstick, as long as you follow the rules.