AGAs all over Europe are going out due to a European 'cleaner fuel' regulation. Read about it here :

Use Fuel Set in your domestic heating oil tank and keep both your Aga and your central heating boiler soot free, saving the cost of the unscheduled service engineer visit. Use just one 500ml bottle each time you top up with 2000L, or save even more by buying in bulk. (Double dose on first application)