PayPal has gone live with its mobile payments system in the UK. But unless you are in the market for women's fashion, it might not be a lot of use to you just yet.The free app is available for both iOS and Android smartphones, both linking directly to your PayPal account. Once you've done that, enter a PIN number select the option to pay in store and a unique barcode will appear. That code is scanned by the store either at the till or via an iPad (how very modern). Once that is completed, your goods are bought and paid for.So all good then? Well, not quite. You see, this is a very limited launch, limited to the Aurora fashion chain, which you might know better as the Oasis, Karen Millen, Coast and Warehouse clothing stores.This isn't contactless payment, it's actually an app-based system that should offer more flexibility in terms of phones. However, it doesn't offer the same reach in terms of stores. That should change as PayPal rolls the technology out to other stores, but this is likely to remain at larger high street outlets rather than your local newsagent in the short-term.Although saying that, this system does save retailers money in terms of new payment systems, so it could filter down to small stores if PayPal InStore actually takes off. A lot of people use PayPal, so it is certainly a system with potential.