I will be traveling to the UK soon and I will be carrying along my international drivers license. Is the license acceptable ID to use when going out with friends or will I need my passport?
An international drivers license is for convenience of translation from your actual (Lebanese) drivers license.
Your Lebanese license is the real one, but the reality is that outside the middle East, few people are able to look at it and understand it. Nor will most people in the world be able to verify its authenticity. The IDL translates your DL information to multiple working languages and provides some assurance that someone else familiar with Lebanese drivers licenses agrees the license is valid.
Clearly this is not an ironclad system but it helps with suggesting authenticity.
To answer your question, you can try using your IDL, but also present it with your drivers license. If I were you, I would then be ready to display a passport for confirmation. After a few times, you'll learn which is sufficient.
An IDP is not an ID. Your passport is your main id when traveling outside your country. A drivers license is sometimes an acceptable back up. An IDP is only a translation of license information and is not an acceptable id by itself. It must be accompanied by your DL (which as mentioned is only a back up form of id).