Anyone know what it is? The Megablade manual that came with my car says 3/8th UNF so went and bought stud and bolts in that. M10 doesn't fit either.

3/8ths unf aint cheap so might use the stud at least.

metric fine thread, think its either m10 by1.25 mm or maybe m10 by 1.00

As above M10 1.25 is the most likely on Japanese stuff.
Steve.

It is M10 fine...

Steve

Just my luck nowhere local has them in stock and min order is a box of 50. Was hoping to fit it tonight.

Give me a call on 01449 736633 with your address and I will send you some original blade ones F.O.C
regards
Andy