Alright I shouldn't have done it in the first place, But I stuck the sump on with cork rubber gasket and aviation gasket goo. After a while it started to weep again so I tried to get it off. Hammering didn't work, I struggled to get a sharp flat blade into it.
So i came with the idea of spraying parts of it with Selleys Gasket remover, about 50% of the sumps edge. I left it for 45 minutes and when i came back the sump was laying under under the bike