Astra G - Fuel Tank Mountings [Hatch,Saloon,Coupé,Convertible,Estate,Van (F07,F08,F35,F48,F67,F69,F70)]
18. SCREW,HEX.HD.,M8,FUEL TANK TO UNDERBODY - part # 13209785 (x4)
19. NUT,CLAMP,M8,FUEL TANK TO UNDERBODY - part # 9202469 (x4)
23. STRAP,TENSION,FUEL TANK SECURING,RH - part # 24408506
24. STRAP,TENSION,FUEL TANK SECURING,LH - part # 24408505
25. STRIP,DAMPER,FUEL TANK STRAP,RH - part # 90571734
26. STRIP,DAMPER,FUEL TANK STRAP,LH - part # 90571733
28. PLATE,PROTECTION,FUEL TANK - part # 24408878
Probably not a good idea to remove the fuel tank cover plate as it can become corroded around the fuel tank, so you will have to ascertain whether one of the straps has become damaged or just a nut and bolt is required to resecure the cover.
You will have to be careful that the tank cover is not 'flapping' about putting too much pressure on the other side otherwise there's the possibility it may shear off completely.
It's more likely that one of the straps has corroded (probably the drivers side looking at your photo) which is still available from GPS (http://www.genuinepartsearch.co.uk) at £27.06. The clamping nuts and bolts also available from AutoVaux.
Yeah I believe so Carl, got a friend to get it attached back up. I don't know if your know but my EGR has a balnking plate where would I locate the wires that normally go to it, as I cant see them anywhere?