If you are over 30 and have allergies you will know that some years allergy friendly chocolate is everywhere and some years there is nothing. It's the same with most foods. You find a food you love and then suddenly it's gone! There are currently several on the market. Plamil are excellent and it is thanks to them that I have been able to try mint chocolate, chilli chocolate, orange chocolate without the fear there maybe a trace of an allergen in the food. Their labelling states that no nuts are used in their factory. Their plain "milk" chocolate isn't great, but their flavours are fab! Similarly, if you are a diabetic, you will also find a range of sugar free which are made with Xylitol rather than artificial Sweetners.
Another great brand are Kinnerton. My family all agree that their regular chocolate is no green and blacks or Cadburys, but that their allergy chocolate whichis dairy, egg, nut and wheat free is brilliant and good in cooking!
The last company I rate are Celtic chocolates. They go to great lengths to Make sure their chocolate is cross-contamination free and most major supermarkets stock them either under the Celtic brand oras an own brand chocolate. I've taken a picture of an ASDA wrapper so you can see what I mean. Sainsburys do one with rice crispies in which I love. At easter these companies ensure we can have an Easter egg which is something I often went without as a kid. Fab!