If I decide to go down the desktop route and get a imac over a Mac mini, has anyone successfully transported them between houses / overseas or is that too risky?
Keep the original packaging, and it should be fine when transported with the same care you'd take with any other valued, delicate personal possessions.
It's about like transporting a TV or other monitor. Just make sure it is Packed well and that it's not dropped or shaken too badly in the move. The original packaging is the best way to ensure it makes it safely.