Dear Sir/ Madam
Ref: tickets for [event] on [date]
On [date] I purchased [xx] tickets from you for [event]. On [date] I advised you by phone that the tickets had not arrived. Despite this, they failed to arrive before the date of the [event].
I was left with no option but to purchase replacement tickets from [xx] at a cost of [£xx].
By failing to deliver tickets on time you are in breach of contract. I am therefore entitled to claim the cost of replacement tickets from yourself. I enclose a copy of the receipt.
Please refund the full amount of [£xx] to me within 14 days or I shall refer the matter to the small claims court in accordance with the Civil Procedure Pre-Action Protocol without further reference to you.
As this is a formal letter I must refer you to the Practice Direction on Pre-Action Conduct and in particular to Paragraph 4 concerning the Courts powers to impose sanctions for failure to comply with the Practice Direction.
I look forward to hearing from you.
[Your name here]