A friend of mine has just got nearly £600 back from the tax man using a company called refunds direct I have been in contact with them and it seems that I may be in for an £800 rebate. Its all to do with a little known child benifit that predates childrens tax credit I think there is something like a maximum of £1500 possible available.

This only applies to you if you had children between April 2001 and April 2003

Give their survey a try you never know https://www.refundsdirect.co.uk/survey/