Website/Store View scope help

Question

We are developing a website with the following requirements:

1. You can choose "United Kingdom" or "USA" when browsing the shop. This shows different currencies (GBP or USD).
2. Products only entered once in admin panel, shared across both "UK" and "US" (ie. they have the same products).
3. Different stock availability because of different fulfillment centres - US orders are fulfilled by a different warehouse to UK (warehouses are in different parts of the world). UK warehouse may have Product A in stock, whereas US warehouse may not, in which case UK customers should be able to buy the product but US customers should not.

Currently our set up is one website with multiple store views, one store view for UK and one for US. Using this module http://www.magentocommerce.com/magento-connect/store-view-pricing.html to set different fixed prices for each currency (ie. not based on conversion rates)... £0.99, $0.99 etc.

However we have hit a roadblock at the stock issue as Stock Availability/Qty is a Global attribute in Magento and cannot be based on different store views.

We would appreciate any help on how to go forward with this. Is there any way we can stop Stock Availability from being Global? Should we create our own attribute for Stock and use that (messy)? We really don't want to end up having to create separate Websites for each US and UK as this means products would have to be entered multiple times.

Thanks so much for any help anyone can give.