Recommend a locum agency that isn't charging £250+/session

We're spending between £180–240/session on locum GPs through agencies and it's becoming unsustainable. I know some practices go direct or use different platforms (Lantum, etc.). Has anyone had good experiences with a genuinely fairer pricing model? We're in the South East so availability is always a challenge, but I'd rather pay a locum more and an agency less if possible.