The main FHIR site has XSD's which you can import using studio. They may need a few tweaks on the way in but nothing major (if I remember correctly it doesn't like narrative)

From these you can build resources which confirm to Care Connect profiles. 

I'm not aware of any NHS guidance on FHIR Messaging except for Transfer of Care but I'd recommend this presentation on FHIR Messaging 

Simone Heckmann’s presentation

What DSTU2 flavour of FHIR would this support? 

Can you produce Argonaut (USA) or CareConnect (UK NHS) profiled resources?