Remember CATIII is a hell of an expensive piece of kit with high running costs. Southend has a good weather record so I doubt it will be in the plan for the near future. It's just bad luck today and probally tomorrow.
Expensive to buy but running costs are not as high as you imply, the tolerances are tighter but modern equipment is a lot more stable these days. Maintenance isn't any more onerous, still requires 180 day flight checking as with CATI ILS. The only higher costs are down to running two transmitters at the same time for hot standby.
