Orders will be available to collect from the flagship retailer at 6pm the night before Android smartphone's release date of May 30.
Customers who have pre-ordered the handset with selected third-party retailers will be able to collect their phone one hour later at 7pm. Specific stores offering this incentive have not been announced.
Samsung vice president Simon Stanford said: "We've had an overwhelming response from our retail partners and customers alike since announcing the Galaxy S III on May 3. So we wanted to delight our customers and reward them for pre-ordering by letting them get their hands on the device a day before anyone else.
"We believe we have created our best smartphone yet, designed specifically with daily human needs in mind, and we are proud to provide our customers with a truly unique mobile user experience."
Samsung's Galaxy S3 comes running Android 4.0 Ice Cream Sandwich on a 4.8-inch AMOLED screen, powered by a 1.4GHz Exynos 4 quad-core processor. Other features include an 8-megapixel rear-mounted snapper and voice navigation.
The handset will be available for £499 via Samsung directly. Major UK operators including O2, Three and Vodafone recently announced their pricing plans for the device.