Now that I've uploaded Board Horde to various sites, I thought it might be useful to others if I share a few findings.
So, Newgrounds was the first place I uploaded to. I was quite surprised to see the Clay.io ads worked here, as I'd heard that many people had struggled to get results. Although its playable on my ipad, occasionally I find it freezes on the loading screen (I put in a fallback to try help with this; if the preloader reaches 100% and 30 seconds have passed it will move straight to the next layout rather than waiting for touch input). Also on some occasions the audio sounds slow and echoing for an unknown reason.
Clay.io was the next place I uploaded to. I'd advise everyone to give clay.io a try as it allows you to put in useful analytics (such as tracking amount of users, how long people spend on each level, how many view the ads etc). I did have problems getting the uploaded game to work on my ipad (even though the only difference between it and the Newgrounds one was it was exported for Chrome instead of html5). On ipad the game would reach 100%, then begin the countdown again and freeze on 30%. After a full day and about 15 upload experiments which included removing the preloader and all audio completely, I finally got it to work by having it skip the audio preload if its on a mobile device (as a result, there's no sound on the clay.io version, on my ipad at least. Works fine on desktop).
Finally I uploaded the game to Gamejolt. Again, I had problems on ipad/mobile (even though it was the same file). This time it couldn't get past the loading screen as it was only recognising touch in the top half of the screen. I'd heard on the forum that retina devices sometimes detect double the screen width (which might be an old problem) so tried turning retina off, but that failed to solve the problem. I updated to the most recent construct version incase it was a bug, but that seemed to stop any touch from registering at all. Since after 8 hours I couldn't solve the problem, I made that version Desktop only and moved swiftly on.
Another place worth checking out in the lead up to game release is Indiedb. Within an hour of putting up a news article about Board Hordes release, the article got 1,500 views (not so many for the game, though).
Anyway, I hope some of this info is of use to people. Please let me know if you'd like me to share more in future.