Cheaper bulk purchasing *done right* does not mean putting your balls in a single suppliers' grasp.
>"A single supplier should be able to offer cheaper prices than anyone else, due to bulk purchasing."
The supplier itself will be able to get better prices, owing to the size of the orders it is fulfulling for its customer (the Police), but there is no reason why it would feel obliged to pass those savings on when it has a monopoly.
In order for the public sector to receive the benefits of bulk purchasing power, it would have to be the public sector actually DOING that bulk purchasing itself. The fact that it is not being done in-house but has been hived off to some private company that acts only in the interests of its own profit is just typical of the moronic dunder-headed utterly blind and non-evidence-based adherence to free market / privatisation / Washington consensus economic dogma without regard to facts or the least awareness of consequences that infests our political classes with its simple minded thinking. Some things are best done en masse, but that seems too much like "nationalisation" to the airheads in Whitehall, so they instead create a stupid artificial monopoly and hand all the potential savings over to a private company instead of getting those savings for the public body in question. Stupid, stupid, stupid.