Can I be a researcher at a UK university without having teaching duties?
Such roles definitely exist in U.K. universities. For example the University of Southampton has 4 different types of Professorial Grade post, which depend on the balance of education, research, and 'enterprise' which a member of staff might undertake. It's possible to have a 100% research appointment under this scheme. 

However, I don't know if every field uses all the types of post. I could believe that the more specialised research only posts are only available in disciplines where these is a reasonable expectation of very high value grants. 

I'd expect similar arrangements to exist in other universities in the U.K.

However, relying on 100% research is a bit of a  risk - with a role entirely reliant on outside funding you never know when those funds might dry up. Some teaching or service component, paid not out of grant funds, could add a bit of consistency and predictability to a role.