I saw these in the Birmingham/Bullring Superdrug yesterday and had to buy them. They were £1.49 for 75ml which I think should do 2-3 applications on my thin/fine hair ;) I remember using something like this when I was 13, it's a wash in, wash out colourent which only stays in for a couple of washes.
I was just going to get the Rich Red, however I spotted a lovely ginger girl on the box of a permanent dye and had the bright idea that I may be able to use one each time I wash my hair and alternate to get a nice ginger... I have no idea whether or not this will work, but it's still an interesting experiment none the less.
I will update you all with pictures of how this worked out ;)