The register
The register lists Circle in London, London as a licensed sponsor on Skilled Worker, an entry that goes back to at least 2026. Rating on the current register: Worker (A rating).
Companies House lists it as Circle Ltd., number 11858925, incorporated 2019: 7 years of filings behind the name. Registered office: 90 Highfield Lane, Keighley, BD21 2HA, BD21 2HA. By its SIC codes the business is in it, software and media. It has traded under other names before, including Circle Platform Limited, Wesafe Limited.
Holding a licence is the expensive, slow part done. For Circle the question each time is only whether the role and the pay fit the current rules, and that is checked per vacancy.