easy peasy mate , i charge £35 for this ,

Get a angle grinder with a 1mm cutting disc and cut the wheel well out just befor the radius where is dropps down ,

Get a sheet of steel , ( i use 1.2mm , but 0.9 is fine ) cut it into a circle about 10 mm bigger than the hole u just cut in the boot floor ,

Place on hole and tack into place , stitch weld arount the whole lot , inch at a time to disapate heat

I use Grey stripe pannel sealer on the under side of the car to seal it all away from the elements , and then primer , Obviously a lick of body colour would be the finishing touch .