Thanks for the suggestions guys, quite a mix there.
While there are some nice hats out there, I can't see me bringing myself to wear a £100 or even £50 hat for working in!
It is going to get trashed, stained, covered in oil, grease and paint, and put through the wash (if it is lucky).
I do try and apply sunscreen to arms, but around the neck and face is somewhat of a pain as I find the dust and muck sticks to it, it stains your clothes, washes off in the rain or with sweat.
Doesn't work too well on top of your hair either!
Might try the legionaries hat thing, probably look like a bit of a wally but hey, if the cap fits…