Anyone got any tips on the best way to cut perfect lines in stainless steel sheet??????

This is strong stuff!
Unless you have access to a guillotine or know of a local engineering company I always use an angle grinder with one of those skinny cutting disks.
I find if you clamp a straight edge to the metal and use your grinder guard as a guide this works well.

Yep. I use a guilotine for thin stuff and plasma for the thicker. Stainless eats up saw blades. Grinder may be best if you dont have access to these machines.

time to find someone with guilotine then, me thinks

take it to a sheet metal fabricator, they'll do it for a few quid.

rich i know lad who works at fabricator in cleck will do it for beer tokens