Companies more and more, are asking employees on long term sick, consistently sick to visit the company doctor.
The legality of this maybe explored soon, when company doctor and employee doctor reports conflict , and company take action .I.E Fire Employee.
maybe you should seek advice fron a Union on this issue.Doctor is stating you are sick , and unavailable to work, and company disregard this recomendation, I wonder have they checked legality of their actions.