Small and local
Housing Cooperative tenant here - couple of hundred tenancies:
We have Dave with the Van for minor repairs (flush not working, gutter fell off in the wind, fence fell over &c) and triage of more major work.
Contracts with a gas fitter, electrician, plumber and roofing/larger build jobs contractor including emergency call-out
Cyclic maintenance (new kitchens/bathrooms/doors/windows) jobs go out to tender, usually bundled into 10 house lots.
Works for us and the transaction overhead is a phone call to Mavis. Nothing like £40 per household!
Edit: QA contractors have to be on the qualified list held by the housing management agent. Published criteria and appeals process if any company refused &c.
Why so large a scale one asks?
Coat: mine's the one with a copy of E. F. Schumacher's volume in the pocket