I am 16 in August and I would like to go away with my boyfriend after my birthday. We have been together a year and a half so we are mature teens. I wish to stay in england but I would like to know if many people accept people of our age.

How old is boyfriend, and where in UK would you be staying. 16 year old can not rent motel or hotel rooms, can not rent cars and so on. You would have to be traveling with a teen travel group.

And I don't know any good responsible parent that would let their 16 year old girl travel on vacation unsupervised with their boyfriend.

My boyfriend will be 17 by August. We are responsible. Most teenagers are steroetyped to being arrogant and bad people. We are not like that.
We didn't mind on where we would go just a place to get away as we have gone through many things e.g deaths, etc. and it would be nice to get away from it all.
Our parents are very responsible and agree with not going too far and only going for a few days.

If your parents agree to it, then it is OK, though I wouldn't agree if I was your parent.

As noted, though, you are limited since you can't legally rent a room on your own.