If you search for a show using the search button, it doesn't find HD alternatives for anything other than BBC1/BBC1 HD. ITV HD and Channel 4 HD are ignored.
But assuming it has noticed, when you go to record the whole series it gives you the option of recording HD or SD. Choosing HD does nothing but take you back to the "record whole series" screen.
As far as I can tell it does actually schedule the HD recording, it just looks like it hasn't! (If you select SD recording tho, it puts little record icons next to the dates down the left, and then menu option chances to 'cancel series recording').