I have copied here for the benefit of others, the content of an email I sent to you earlier.
You are in the right area, those are thermal magnetic miniature circuit breakers on the control panel. They are not not fuse holders.
It is possible that one of them has tripped because of an overload condition as would happen in a domestic situation.
Have a look at the toggles in the centre of each circuit breaker to see if any one of them, especially one with a lighting symbol (a circle with a cross through it) looks different. If so have a go at resetting the toggle so that it resembles the others.
These thermal magnetic miniature circuit breakers have been known to go faulty for no reason. If you suspect this is the case please get back to me and I can direct you to a supplier where the cost will be 90% cheaper than Hobby. They are a simple push-fit into the front of the control panel. It is also possible that a wire has come off its connector somewhere.
Having since spoken to you on the phone, I would suspect the problem with your Thetford toilet is that the pump is jammed. This would be confirmed by your diagnosis whereby a new fuse inserted after removing the cassette, blows again as soon as the flush button is pressed. This can be as a result of using pink flushing fluid, which if left in the system undisturbed too long, can go all thick and congealed, resulting in the pump impeller seizing. As I recall, the pump is accessible in your van by removing the toilet roll holder.