As for stopping ticks, Hanneke is spot on - you need a barrier. It doesn't seem to matter that much what it is, although I'm sure the right smells will distract them. But I have found that on days I'm completely plastered in sun cream, they tend not to latch on.
MickTor - a bite like that could be a cleg? I've had a few bites turn nasty (although nowhere near as bad as yours) over the last couple of years, and I'm sure that's what's bitten me.