You are better buying a bottle that states 100ml on it. You certainly won’t be permitted to take a 120 ml container. Security staff are allowed to make an informed decision on whether the container is 100ml if it does not state 100ml on it(at Manchester definitely)
If you put them in a clear plastic bag and present them out of your main bag before Security screening you should be fine. They may do a liquid test on your bag. It’s perfectly normal Airports are familiar with all Vaping hardware and juice.