Problems with tesco direct/double up on clubcard vouchers

RSJE

Hi, I originally posted this on the grocery board, but figured this was a better place for my querey!

Hello, this is my first post, so please be gentle with me! and apologies in advance for the long post...

I recently doubled up my tesco clubcard vouchers to purchase a baby car seat whilst they were on special offer in tesco direct. When i came to purchase the seat online, only £60 of the £80 vouchers i had worked. Here is where the saga begins. I rang the store, which ended up at central customer services, who told me it was a store issue. They put me through to the store, who didnt answer the phone. I went to the store, queued for 30 mins to see customer services, who told me it was a clubcard issue. Came home, queued on the phone for 30 mins to speak to clubcard who told me it was a store issue.....by now it was late, so I didnt return to the store that night. Next morning I went back to the store, checking stock availability before i went, i discovered that the car seat i needed was out of stock! one hour later the store agreed to swap the £20 for a gift card, but refused to compensate me for all the inconvenience - they did admit that there was a problem with the club card vouchers at that time. The problem now is that the 25% off deal is about to finish, and the car seat has not come back into stock. This means that the seat will now cost another £30ish - i think that Tesco should pay this extra, as it was problems with their vouchers, and their inability to resolve the original problem quickly that meant I missed out - i did have the seat in my basket! Would you agree with this?

Has anyone else experienced this with clubcard vouchers?
is anyone aware of any policies that Tesco has regarding compensation to customers that i can use???

thanks very much for reading, and any advise greatly appreciated.