On the question of eggs, the reason vegans don't eat them is that all male chicks are killed instantly at birth.
Obviously five pound notes aren't the only product that is sourced from animals. Animal products are everywhere - there is even pig fat in tyres, I believe. If you're a vegan, you can only do the best you can - the vegans I know avoid eating honey or wearing leather or wool or using cosmetics that have been tested on animals or include animal products. But there is only so much you can do. It's not, after all, the fault of vegans that so much produce is derived through animal cruelty.
I've never quite understood why a desire to avoid animal cruelty is the subject of so much hostility. Most people who eat meat would be horrified at seeing someone kick a dog, for example, or at an animal such as a lion being shot for someone's entertainment. But then they get very very angry at the idea that someone should want to avoid being complicit in animal cruelty by not eating meat or dairy.