I work as a UX team of one myself, and I know how this feels. I'm the only one in my company who does what I do, and literally everyone else here has some sort of peer group to work with. Devs, QA, managers, IT-- they all have at least one counterpart. I do not.
I'm also one of those people who does best feedback on a regular basis. I need to know that the work I'm doing is valuable and helpful. I need to know that I'm making life easier for the team with which I'm working.
What's worked best in staving off some of the isolation is to reach out and request feedback from other teams on my work and process. At the very least, it helps me feel more connected to the rest of the organization. It also helps build bridges to other parts of the business and gives clarity on my perceived performance and limitations. I work for a company where UX is still a relatively new concept, and reaching out to other teams helps me to be a bit of an UX evangelist.
I hope that idea is helpful!