Bad Oil leak. Need help

[GraeV11]

Replaced my lower sump gasket towards the end of last year as it was weeping oil. It started weeping again recently so replaced it again thinking I had screwed the repair. It is now worse; went out for a blast today and went a tad cold when I returned and found splats of oil all over the left side of the rear tyre. Getting a bit Pi55ed off now as is the wife with the spots of oil all over the drive. I am 99% sure that the oil is not migrating from anywhere else. Has anyone any tips as to best source of gaskets / sealants or techniques for getting this right (before I do something stupid like tightening the bolts until they snap)