Boil the vinegar with the sugar, peppercorns, allspice berries, bay leaf and thyme for a couple of minutes, remove from the heat and allow to cool.
Peel and finely slice the onion, deseed and finely slice the peppers and slice up all the chillies.
Place the chillies and vegetables in a bowl and pour over the vinegar. Stir, and leave overnight. Stir again before serving. You can store any leftover pickle in a sealed jar in the fridge.