isn't something your designer can do - that's down to you, or rather your products.
One of the main points I stress to clients is the fact that an e-commerce site is visible all over the planet, and you must remember this when designing the site. If you don't want to receive orders from Japan, or anywhere else utside the UK you must say so, loud and clear, on the homepage.
If you do want international orders then be prepared to handle them. People who buy online expect almost instant gratification - goods must be delivered speedily. Apart from that, the site must be able to handle different currencies, which will be the case if you use PayPal credit card processing. Remember that for credit card payments you'll need a Paypal business account - they don't provide the service for normal accounts.
It's impossible to tell you what will make the site satisfying to visitors without knowing a good deal more, but your site designer should be able to advise you on that aspect of the project. He/she will pay careful attention to navigation and visual clarity - soft furnishings need lots of images, I imagine, and the quality of these will be critical - people buy with their eyes.