What to do when a multi million $ company doesn't pay up?

A very good question. Maybe you can help and answer with some legal know how.
It all started last year. I was so happy to have my dolls up for sale in Fabrica Features Benetton Shop in Lisbon. Apart from the great kudos, but I must confess that as a teenager I absolutely hated Benetton... too many pastel shades for a young punk rocker, I thought it would be a great chance to get my creations out in the big wide world. They were taken on a sale or return basis which with hindsight I would never have done but each opportunity must be explored and taken...or so I though!
I've now taken back my stock and have been awaiting payment for over 4 months. All receipts/invoices are legal but they say otherwise. After speaking to the relevant tax offices it was said that on imported stock they are exempt from paying the VAT what they need to do is pay their equivalent tax to their country's financial department. So why they need it is beyond me. Basically you would need a VAT number only if you were trying to get a reimbursement from the UK's tax office which they can not do. From what I understand a company that exports to another EU country does not need to provide their Tax registration number as this is only relevant in their own country.
I know that this Benetton shop in Lisbon is a franchise but it does leave a sour taste in my mouth regarding the company as a whole. It's just really sad when a large company like Benetton tries to tap into the handmade, art and craft market and actually explores small makers like myself.
Oh well...that'll teach me for not stick to my ethos and teenage beliefs!