Managed to find both phones in a shop on Friday.
I am going with the One S next week for the simple reason that it can comfortably be used one-handed. The One X is just too wide to feel comfortable in the hand.
HTC Sense works on the Desire - you just need a HD ROM. Plenty of those available at xda-developers (Modaco is currently well behind). My current favourite is here and has taken over from MCRr9 as my everyday ROM:
I think I have downloaded everything I need. Will give it a go when I get the time.
The only item I can't seem to find is the black/grey striped wallpaper for the scrolling theme. It is not in the dropbox. Do you still have a copy please?
If you just want to flash a new boot image, search the forums on modaco or xda, there is plenty of guidance there. (Don't confuse the Splash 1 screen with the Boot Image. The splash 1 is the fixed image you get when the phone is first turned on. This can be change if you have S-OFF. The Boot Image is the 2nd (animated) image during the boot process)