We might have to put this to a vote. Some of us think that 3,17 are combined to be a particular 10, while others think 3 and 17 are both different 10s, sharing the same letters. Both fit. I chose the former along with a lorra other people, but it's true that the latter makes the homophone a bit better. I guess we will find out next week.
I'm afraid I don't see the connection between 17 and 27 with either solution of 17. Unless I have 27 wrong as well, but my 10,27 does fit the mini-theme represented by 11 and 26.
I'm actually surprised 27 wasn't used in the wordplay for 17. As an American, I make a mental list of UK terms employed in crosswords, and I recall 17 occasionally arising as a solution via "17 27" wordplay.
In 17, I took the definition as being '3', i.e., it's the same 10 as 3. I'm not sure the surface is that convincing either way, but I am beginning to think you may be right.
I just googled 17,27 assuming ChrisE and geeker were right, and apparently, they were indeed a 10,27. They only lasted a couple of years, so I will use that as an excuse for my ignorance (as well as lack of interest). So I now agree that 3 and 17 are anagrams of each other. I wonder if Paul knew of the "rabbit hole" that many of us dived into. Perhaps that's why he chose 17.