You’ve got a couple of options when it comes to transport rom Ubud to Kuta.
Bus from Ubud to Kuta run regularly and there are a about 5-6 set departure times everyday.
How much does a bus from Ubud to Kuta cost? About 50-60,000 IDR ($5/3pounds)
We got a taxi for 2 people from Ubud to Kuta and had a very nice and knowledgeable driver who happily chatted away to us for most of the journey pointing out good things to see and talking about Indonesia in General.
How much does a taxi from Ubud to Kuta cost? We paid 200,000 IDR ($20/12 pounds) for two people in a private taxi.
This is the cheapest price we came across (although we bargained down from 250,000 IDR, it seemed fairly quiet and we left early morning, so potentially it depends of the season and time whether you can bargain down this much).
It’s also worth noting you can easily jump in a metered taxi if you are traveling from Kuta to Ubud, it would probably be slightly cheaper but in the return direction there are very few metered taxi’s around. If you do this make sure it’s a Blue Bird Group taxi, as they are the safest and always operate on meter so you won’t get ripped off.