How can I accurately rotate UVs ?

I have been doing some UV work and I am wanting to rotate some UV islands. However when I select rotate for the UVs I seem only to have the option to use the rotate tool ( ie the black line with little arrows) and I cant see any way to numerically select a rotate amount. The tool is fiddly if Im looking for example for exactly a 90d rotation. Is there some way to rotate UVs by an exact amount rather than fiddling around with the rotate handle tool?

Press R then type 90 to make a 90 degree rotation

Im such a dummy! You know that had crossed my mind but then I told myself it couldnt be that easy! Many thanks ! Ill mark this solved.