I would strongly advise you to comply with your employer.
They owe you a duty of care, and if they fail in that duty not only will you become ill again but they will be liable in law should you want to sue.
Just tell the company doctor that you are fine now, your GP who knows you and your medical history well recommends you return to the workplace and you are eager to return.
It may be that you go back to work on reduced hours for a week or so to 'ease you back in' as it were, but that is nothing to worry about.
Remember, this is to protect themselves against a future claim, nothing more.
It would be very difficult for the company to sack you and they know you would have grounds to pursue an unfair dismissal if they did.
Play the game. You'll be fine.