I know this is an old thread, but I was about to refill my Sarsons vinegar bottle this afternoon, only to discover the treachery inherent in the newer cap design :(
I found this thread by googling the problem, and am about to attempt a solution: heat the Sarsons bottle upside down in a cup of boiled water and then use oven gloves or a tea-towel to remove the softened lid. Wish me luck..