In BG2 'rest until healed' is an option that can be selected in the settings. OK.

In BG1 I cannot find any way to turn this level of healing on despite what appear to be references to this in various help pages on the net. It does seem that there is a relationship between the quality of a room at an inn and the hit points gained but nowhere can I find anything about the wider 'rest until healed'.

Can anyone shed light on this?

Thanks!

For Baldur's Gate 1: Enhanced Edition:

Options -> Gameplay. Scroll the left pane downward to reveal "Rest Until Healed". Beware, as noted on https://baldursgate.fandom.com/wiki/Rest, this is merely a shortcut to keep choosing "Rest" until party members are fully healed, so your party might rest for far longer than normal. If you have a timed quest in progress, you might prefer not to rest multiple times repeatedly.