Nice loafers Alex. Great colour aswell.
I think though of all various shoe types, loafers are the hardest to buy without trying on. I do believe a loafer should be tight to begin with as it will expand with your foot, I also find that suede is softer than full grain leather or shell and has a bit more give.
Based on my experience I think if you are experiencing heal slippage now it will only get worse as you wear in. My own experience of c&j g width shoes are that they are very wide. Hope they work out for you.