(Mr MC posting)
ref: "each force buys its own" and "no wonder public sector…"
Here in Thames Valley they arent bought consistently at a force level. Different police areas buy different bikes, and then change their requirements as the years go by. I was a "pro active cycle officer" on blackbird leys a few years ago and rode cheap £200 Giants 8hrs a day, chasing twoccers and plastic-yardie drug dealers down alleyways, great fun (probably the most fun Ive had in the job). Other more established teams had nicer bikes, and oxford city centre officers currently have ~£500 Marin hardtails. We proved cheap bikes were a false economy by hammering the giants, but not sure if "my" team ever got better bikes. Each area will have a business manager who runs things and I'm not aware of any accepted force-wide or nationwide spec requirement (such as they have for standard response cars for instance). Probably seen as part of local spending to solve a local problem rather than a forcewide deployment.
theyve introduced cycle skills courses which are fun but demeaning for serious cyclists, but common sense and organisationally reassuring as they were putting people out on bikes who could barely ride a bike.