The law in the UK says that you need to be at least 16 before you can consent to have sex. This changes to 18 if the other person is someone in a position of trust - like a teacher or doctor. Once youre 16 you can legally have sex with anyone older than you, as long as both of you feel okay with it.

Is it legal for a 16 and 20 year old to date UK?

There arent any laws around being in a non-sexual relationship where one person is under 18 and the other over. Once you turn 16 its not illegal for someone to have sex with you no matter how old they are.

Is it illegal for a 16 to date 23 UK?

In the UK there is no law stating it is illegal for a 23 year old to date a 17 year old. As you are 17 and a young adult, you are old enough to decide if you want to be in a relationship with this man. Its important that both partners consent to the relationship, and that they trust and respect one another.