Thanks guys,
I guess the Bios / boot routine etc does a check on the eprom to see if the region matches. I knew about removing tabs etc from the PAL N64 but luckily I don't need to as have a US console as well as PAL.
I knew you lot would know.
I'm 90 carts away from a full PAL N64 set and Bad Fur day Pal Still sells for £55+, was thinking get a US Cart and swapping to a PAL case, Not to fool anyone just for my own pleasure of saving some cash.
J