Parking in a disability bay is only illegal without a blue badge if there is an official signpost stating it is a disability bay.
If just painted on road it is only advisory.
If its been there a year then it could be classed as an Obstruction of the Highway under the Highways Act 1980. Contact the local council they have the power to order an offender to remove the obstruction. If its not removed within 21 days of the notice the local council can remove the obstruction. The owner has probably died, been arrested or whatever for a car in that condition to be abandoned. But a disabled may is for any holder of a blue badge, not an individual.
Unless that disabled parking bay has specific marking saying "this bay can only be used by X" then any blue badge holder can use it. Granted the blue car that is currently parked there isn't displaying a blue badge, but to specify it's a "child's disable parking space" is incorrect.
Parking in a disability bay is only illegal without a blue badge if there is an official signpost stating it is a disability bay.
If just painted on road it is only advisory.