Hi Jordi,
Have a look at the website_quote module from Odoo.

When installed, this module allows the creation of a  button to help you view the quotation online - this button brings you directly from the Back office to the Front office.

Maybe you can analyse the behaviour of this link and replicate it to your needs.
 

Thanks Will,

I based my work on website_quote and worked fine.

return {
            'type': 'ir.actions.act_url',
            'target': 'self',
            'url': '/shop/product/%s' % slug(product_template)
}

The trick was to set the type to 'ir.action.act_url'

Regards,

Jordi