I want to learn how to ride (UK)

Hello, first of all as the title suggests I'm from the UK and I want to learn how to ride a motorcycle. I'm 18 and can drive pretty well (been driving for around a year) and I've just always wanted to ride a motorcycle. I haven't really done much research into it before now because I don't know anyone who rides a bike and when I do look into it, the whole process seems far more confusing than learning to drive.

First of all, what do I need to do to get started with motorcycling, I understand many people get Scooters at 16 and trade up to a bike later on but I want to get to riding motorcycles as quickly and as cheaply as possible. Do I really need to buy a Learner bike? If so, which model is recommended?