All BBC channels are now available in HD, including English regions, BBC ALBA and BBC Parliament. 

You can change your nation or region by selecting Change location, located at the bottom left of any BBC iPlayer page, or by heading to the Settings menu on the BBC iPlayer app.

Live channels can be found under the Channels menu, choosing the channel and selecting either Watch live or Watch from the start.

If the picture quality is poor when watching in HD, have a look here for more info: Why is HD picture quality poor sometimes?