Right on cue Microsoft has started selling the Surface 3 LTE directly through its own store in selected European markets. We heard a few weeks back that the UK, France and Germany would be coming online and orders are now shipping.
In the UK, local carrier, EE, is providing a 4G SIM card in the box. It's important to note that this appears to be some kind of partnership, not Microsoft selling the Surface 3 on contract. You're still paying outright and you're still buying it unlocked and contract free.
Also included with the Surface 3 LTE is the free one-year subscription to Office 365 Personal. The 64GB/2GB RAM model will run you for £499.99, while the 128GB/4GB RAM version will cost £579.99. Order both now at the link below.