I don’t think there is a middle bit. Nurses and vets tend to do all of those between them, e.g. anaesthesia, radiography are all things as a vet student we’ve been taught from day 1 of the course, and commonly nurses monitor anaesthesia during procedures. As a vet you can also specialise further into those and other branches, either with certificates or doing internships and residencies and usually if you do that you’ll probably work in a referral vet hospital rather than a first opinion clinic, but being a vet comes first - I think there are also certificates or similar for vet nurses. “Vet tech” to my knowledge is a vet nurse but in America. Some clinics also have animal care assistants, who help care for the inpatients etc but can’t get as involved with the medicine side as a qualified nurse or vet - you don’t need any qualifications to become one.