First of all, if you'd already seen a post saying they pass on fanmail, I dont understand why you'd ask if they do or not?
Anyway...
I have sent numerous requests to the MEN Arena , and never had a reply. I wasnt sure whether it was just the people I was writing to, or if the arena didnt pass it on. So in 2004 (I think it was) I contacted them, and was told categorically "No, we do not pass on mail to performers. It will either be discarded or returned to the sender if there is a visible "sender" address". After this, I no longer sent requests there. However upon joining this forum I saw that thread you mentioned, that says they do. So again, I contacted them, and again, I was told the same thing. I posted it on that thread, but it muist've been deleted at some stage as its no longer there.
You asked a question, and I answered it with the information I had direct from the MEN Arena. If people have had successes from there then congrats to them, but the above is what I was told by the MEN Arena, and after around 6 failed requests to that venue, it seems to me pretty strong information.
If you dont believe me, or choose to try, thats your business. I just answered the question with the information I have.