Allotments are generally council owned and rented to the public in the area rather than being private. It's normal for allotments to be gated so I've added it as reported, together with access=customers to the gate and all relevant paths. I've also added the name Sketty Road Allotments as used at https://governance.enfield.gov.uk/documents/s37878/P13-00212PLA%20Planning%20Committee%20Report.pdf which will make it less likely to be assumed to be a public park.