I said do not put Halfords car paints over appliance white for a good reason....
Appliance white is a enamel based paint for kitchen appliances, this is for the hard wearing properties of enamel paints.
Halfords car paint is a cellulose based acrylic paint - that's why it has the awful smell.
Anyone that knows paint will know that you can put enamel over cellulose, but you cannot do it the other way around, if you do, the top coat will craze and crinkle far worse than any orange peel affect.
So the way forward is to stick to one paint system only, either car spray paints, plasticote paints, humbrol or whatever, do not intermix unless you have done a test panel first.
The one departure from this is halfords spray primers, as they are going on the substrate (the ship) first, there is not normally any reaction to other paints you put over the top. I use red oxide primer for below waterline, then mask that off and use Humbrol enamels above the waterline, although I am slowly coming round to using Vallejo acrylics, once dry they are purported to be waterproof, but I seal them under a clearcoat anyway.