Chinese crispy beef with minced beef instead of slice steak? I've read up on a fair few recipes for Chinese crispy beef, but they all call for a beef steak to be sliced up, such as topside, rump, sirloin. But I cannot find any info or recipes on substituting slicing a steak with using minced beef instead.  

I presume this is because minced beef is much smaller and won't be "bite-sized", but I've had similar very small sized crispy beef in a Chinese restaurant before and it was fine.  

So would it work out ok using packet bought minced beef covered in cornflour and fried?
Or would something not work, such as the beef wouldn't go crispy etc?
Try browning the ground beef first in a pan (no oil). Dump out on paper towels to absorb the grease.  Use onions and other aromatic vegetables at this step if you like, too.

Then stir fry the other ingredients,  and add the beef to the stir-fry towards the very end of cooking.

Have you ever browned hamburger meat (or whatever texture is the minced meat you speak of)? Ask yourself how stir frying is any different than that.  At worst, incompatible ingredients (whether temperature,  duration, vigor) are fried in different batches and then combined at the end.  You can often optimize by adding ingredients at different stages, such as putting the garlic in last so it doesn't burn and browning meat first so it doesn't burn everything else.

For an Asian stir-fry dish, you don't want to fry in the oil made by the beef, but change it out for cooking oil anyway, or if high temperatures are involved, peanut oil that won't smoke.