It's always great to receive thank you letters:

Hi, My daughter has just come back from a hallow'een party/disco at the Friesland Sports Centre in Sandiacre. She was over the moon and had a great time.  I saw your 'Mr Custard' website on the van and decided to enquire about the possibility of entertaining at her 7th birthday party on March 25th next year from you Fay Trewhella.