..I think you will need to categorise companies more than just '50 employees or less'.
We have only 40 employees yet being a company in the financial sector, with systems classified as 'complex' by our auditors, we necessitate an IT Support infrastructure and by being regulated are expected (and see the need for) extensive Disaster Recovery/Business Continity plans which are regularly tested.
I suggest that you add to your criteria: i) Complexity of systems required and ii) Regulatory Status
I'm not suggesting people only have contingency plans if they are regulated but it certainly encourages people to if the FSA are asking to see it, you could read the 2nd criteria another way as companies who need contingency plans perhaps more than others because their business relies on their systems. A small plumbing firm might be able to start up the next day after a disaster with no IT systems. A small Stockbroker might well not.