I assisted an after school club at short notice. I did it because it was local and within walking distance. It also got me out of the house. However, after being taxed on emergency code, I only brought home £12 for the three hours. If you accept once, they will ring you again to do it. Last time they rang, I had teaching work with another agency, so I missed the call. When they ring again, I am going to say the hours are inconvenient. Usually having tea around six anyway.