In a previous role, we've used LetzLive - https://www.letzlive.org/ - we did a lot of checks ourselves, but they always provided DBS certificates which were sent directly to the school and these always arrived prior to their start date.

We also use Letzlive. I particularly like that they carry out safeguarding training by the BSA prior to arriving in the UK when they have the layover in Dubai. We supplement it with our own training but they're not coming to it cold.

The hold up for us, prior to using an agency, was that they had to obtain a UK bank account and have council tax for proof of address before we could apply for the DBS. It feels more complete for them to have the DBS upon arrival and no more or less secure as we know this is their first arrival in the UK. We check and verify everything else which we are given (inc references - which can be tricky with the time difference!) so we are confident to the same degree as any other employee.