rebus - The Lord of the Puzzles

In 1904 (at the age of 12) J.R.R. Tolkien sent a "puzzle letter" (pictured below) to a family friend; Father Francis Morgan.

What does it say?

^{_{Obviously it would be trivially simple to google the answer, so I want you to promise me that you didn't :-)}}

Answer

The sender's address (top right) was:

Woodside House, Rednal (wood, S, eye, D=500, E, house, {N, A, L=50} in red)

The letter reads:

My dear wise owl Fr. Francis, (M=1000, eye, deer, Y's, owl, France with 'Fr.' on it, hiss)

You are too bad (U, R, 2, bee, A, D=500)

not to come in (knot, 2, sea, O, M=1000, E, inn)

spite of Fr. Dennis. (spit, E, OF, Fr., D=500, hen, eye, S)

I am so sorry you (Hyam, sew, saw, rye, yew)

did not like the (D=500, eye, D, knot, L=50, bike-B, tea, HE)

word 'piano' in my l... (words, pea, note-T, inn, M, eye, L)

...ast letter. So I... (mast-M, letter, sow, eye)

Thanks to Pete and d'alar'cop and LeppyR64 and JNF for help with some of the clues (see comments below).