Snapfish customer service,

I received a snapfish voucher as a retirement gift. The person purchasing the voucher had to buy it in 2 lots because the system wouldn't let her buy it as a whole.
When I came to redeem the voucher I created an account and entered the code but only £10 was credited and the rest had disappeared. I have made into teens of calls and emails to Snapfish - they accept there is a problem but will not credit the account with the missing amount. They have given various incomprehensible explanations as to why this will not be done including the suggestion that passing the voucher between people invalidates it!!
Tried to make a complaint but the person I keep speaking to also says she is the complaints dept so feel like I am getting no where.
Does anyone know if they have a uk based complaints department?