Newbie here.....new to your site, and at gardening, so any answers, please don't make them difficult for me to understand, will you?

I've just moved into a bungalow, with a very mature cherry tree, I would guess 30ft high. Down the bottom of the trunk, in a section, and also at the top, kinda where the branches start coming out, there are bore holes in another section. The bottom bit, to me, looks sort of dead in that place.

The tree is such a beautiful feature in the garden, that the last thing I want to do is to lose it.

Please, please, can someone tell me what I can do to save it.

PS. Now please don't all be alarmed, you gardeners, but as a dog owner, I'm having 'astro-turf' fitted up to, and around it next week. (I did tell you I wasn't a gardener, didn't I?)