Book title

[kmglondonuk]

I am looking for a book I read when I was younger, I can't remember the title but the plot was something like this: There are two children, a girl and a boy (I think the girls name is Nicki) and their Mum gets mugged while on holiday with her boyfriend. The children are left alone and don't know what has happened. They decide to run away and find her whilst on a school trip. I don't remember much else other than the girl is quite feisty and the boy gets bullied a lot. I've been searching for this book for ages, can anyone help?

[remusfan]

sorry i don't think that i have read that book but i will let you know if i come across it! - promise -