Every week a Guardian Money reader submits a question, and it’s up to you to help him or her out – a selection of the best answers will appear in next Saturday’s paper.

Our family is fast outgrowing our hatchback car and we need to add some space for holiday trips. A roof box looks favourite but I have also seen roof bags that are much cheaper at £55. Do these work, or do we need to buy an estate? What works for you?

Do you have a problem readers could solve? Email your suggestions tomoney@theguardian.com or write to us at Money, the Guardian, Kings Place, 90 York Way, London N1 9GU.