relationship between order order detail tables?

what the relationship between order and order detail tables? (checkout workflow)

I've created the checkout for PayPal website standard and ran some test.

I don't understand at what point does the order table update as seems not to be working.

When using paypal standard, the order information is stored to the database when the Checkout form post to the confirm page.

you have the trigger for the store order summary behavior set to use the submit order button, it should use any form post instead.

Thanks that fix the problem

But after the submit button is pressed it passes on to paypal and the customer puts in there card details. What have to do in PayPal to point the customer back to the correct page (approved.php and failure.php) ?

on the confirm page, there is a hidden element that allows you to set the return URL to return to your site.

the problem with paypal standard, though, is that it is not a real time payment method.

Once the user enters the paypal account and selects to proceed with the order, the transaction is placed in a queue to be processed on a first come first served basis and the user is redirected to your return page.

It is not posible at that time to know the success or failure status of the transaction.

paypal standard uses an IPN system to make notification of the order status when it is complete:
https://www.paypal.com/ipn

I've notice during the test the currency shown is USD not GBP is there a setting in confirm page to change the currency or is in the paypal account.

Yes, on the confirm page there is a hidden element that sets the currency, change the value of that hidden element from USD to GBP