In England, is it legal but wrong to smoke in your garden by the hedge so that the neighbour can smell it?

Perfectly legal but you shouldn't be anti-social.

I don't know about England, but here in the Etats Unis it depends on how cute your butt is.

I would have to charge you for advice like that

Not illegal, but disrespectful.
Why upset people unnecessarily?

Perfectly legal to smoke in your garden in the UK.
Problem starts if there are complaints made to law enforcement or council officials under the guise of antisocial behaviour.

So one person smoking - no problem.
Twenty people smoking - might be an issue

It is antisocial - wait until the wind direction changes, i.e. you are downwind of him