Hi Nigel if you don't mind I will go through this one stanza by stanza

stanza 1
great, nice rhymes flows off the tongue beautifully

stanza 2
I would lose 'sent down from line 3' and 'sent' from line 4, helps the flow, read it aloud you will see what I mean.

Stanza 3
line 4 doesn't quite go with the three before

how about 'those that are black as coal'

Stanza 4
I am not sure about the repitition of her name, I would use 'she is' in line 1 then drop it completely from the next two

ex
She is my life force
the blood rushing through my heart
every fibre of my being
And we shall never part

Stanza 5
the repition in line 1 is too much, You could also drop 'No' as it is a little confusing, I had to read it 3 times to get your point

How about 'we shall never ever part'

I would also lose line 3 altogether and chop 'she's' and 'someday' then change Denise to 'she'

stanza 6
last line just drop 'and' at the beginning
(helps the flow)

Stanza 7
Perfect, and referring to her by name again works here, I would leave her name in stanza 1 and the final stanza only.

Overall there is a beautiful message here and I can tell she is a lucky lady as you are obviously a very caring man. My suggestions are just that, this is a poem from your heart so ignore them if you want.

I am stilling giving you 5/5 because I felt it was honest and very heartfelt.