Plastic bottle tops that come on single use plastic bottles are made from PP (plastic 5) or HDPE (plastic 2). PP being the most common material for bottle tops is not commonly recycled. Most household recycling centres will ask you to remove the top before recycling meaning that it ends up in landfill....Another small piece of plastic potentially entering the ocean.
There is a lot of confusion about the recycling of bottle tops, many companies claim that their caps are recycle-able and it's best to leave them screwed on. Honestly, it completely depends on the facility they end up at. They have a completely different melting point to the bottle PET (plastic number 1) and it comes down to the cost of recycling two different componants.
Its best to check locally, but if you are unsure there is a solution!
Collect your caps in a box next to your recycling bags/ bins. When you have a lot find your nearest Lush store and they will recycle them for you.
There are also many charities and schools that collect bottle tops so you can always check to see if there is anywhere local to you.