Several of the major couriers have siftware systems that you can link into from a trading site that allows people to track thier order dispatch and delivery status.
Fedex UK click here has links to 'ebusiness tools' and 'tools for shipping'
The Royal Mail ParcelForce service has a business section for similar services to those offered by FedEx and most of the other big players offer the same or equivalent features where you can link your online ordering system into your business courier account.
It's down to deciding who you want to set up with really, but once you decide on one courier, linking into their delivery systems is possibly the least of your worries. I'd make some calls if I were you and ask some key questions. Explain your requirements and ask whether the company have an available system for business account holders who trade online (or who intend to) that will allow order delivery tracking and can they handle large and small objects.
I've had good reults with FedEx but I know of others who use different couriers and have had simiar outcomes. Then again, wardrobes are not on my list of deliverable goods...