Can I use a UK drivers license as ID in Las Vegas?

Take all picture id as you will have trouble getting in anywhere. Only pic ID will do.

As long as it has a picture and you match the picture and the license is valid, e.g., not expired.

Im not sure about the bars but I work in the cashier cage and to cash your chips you have to have your actual passport no copies.

Sure can. You should have no problem.

Yes, I always my driving licence as ID all across the US and have done in Vegas in the past as like you I don't want to be carrying my passport everywhere.

I'm in the RV Rental business and have dealt with a number of UK customers, and we accepted the UK license with no issue. I never had a customer return saying they had a problem somewhere with someone accepting their license for proof of I.D. If you can get one, it never hurts to have an International license as well.

Yes and I also suggest you take your passport to a local print shop, get a colour copy of the information page, reduced to credit card size. Then get it laminated and keep in in your wallet. I live in South America and use it for my ID. It is even accepted for internal flights as official ID. I have also used it during stays in other countries. I never carry my passport unless I am travelling internationally, going to a bank or to a government office.