The register
The register lists Stack 'M High Limited in Weyhill, Hampshire as a licensed sponsor on Skilled Worker, an entry that goes back to at least 2026. Its rating on the register is Worker (A rating).
Companies House lists it as Stack 'm High Limited, number 04883483, incorporated 2003: 23 years of filings behind the name. Registered office: Scots House, 15 Scots Lane, Salisbury, Wiltshire, SP1 3TR, SP1 3TR. Its filed activity puts it in business services.
A licence says an organisation may sponsor; it does not say it is hiring today. The way to find out is the same as for any employer: the careers page, the job boards, and a direct approach with a UK-style CV that says early that sponsorship would be needed.