Ariston water heater

[billy_mega]

I have an ariston SG 80 MO water heater on the side of my house (holiday house in The Gambia, not UK) and it stopped working. Now, if you switch it on at the double pole switch, it blows the 20 amp breaker at the consumer unit after about 30 seconds of being switched on. I have been trying to remove the heating element to try replacing it but I cannot work out how to extract it. I have removed the thermostat and there is an oval plate with rubber seal round the edges which I assume is covering where the element swrews into the body of the heater but I cannot remove this plate so I cannot get to the element....can anyone help....??

Thanks
Bill