This http://www.noahsarkgardens.co.uk/Wil...ardenBirds.htm
may help with identification. Definitely do not feed it in the manner
you describe or disturb it in any way otherwise it will vacate the nest.
Just keep your distance. It will find plenty of food. You can help by
making sure that predators do not cause harm.

the letterbox is on a garden gate that gets opened and closed al the time,
and now and again we lift the lid and say hello, it seems perfectly happy
about all this
:-)