My thyroid Level normal now.

You can have hyperthyroidism due to an infection which is called thyroiditis or more commonly it is due to an autoimmune disease like Graves disease or Hashimoto's disease where your immune system is attacking your thyroid.  If you have thyroiditis, stopping your medication will not cause a rebound.  However, if you have an autoimmune disease like Graves, you also have antibodies detectable in blood tests.  I have Graves disease and my Endocrinologist said he would not stop the medication unless my antibodies had normlized as well as my thyroid blood tests having normalized.  My Endo does TSH, FT3 and FT4 blood tests, not just TSH and FT4.  So you need to find out more information from your doctor about the cause of your hyperthyroidism and if it is due to Graves disease then he/she needs to check for antibodies with blood tests.  If these are still elevated, then stopping it is not a good idea. 

If you have Graves Disease doctors generally rely on blood tests to check if your thyroid can function on its own without the medication, if you can't the symptoms will gradually return and your GP may do further investigations but more likely put you back on medication again.

I developed Graves and have been on maintenance dose of 5 mg Carbimazole for twenty one months with regular blood tests. I came off the medication one month ago and am already beginning to get the hand shake and 'butterfly' internal effect. Blood test due tomorrow. 

If you have Graves disease stopping without slowly reducing the dose is not a good idea.  If you do some research on the internet you will find out more about the disease.  My GP stopped my carbimazole as he thought it was lowering my white cell count (in fact they are always low to to other auto immune issues I have).  It came back 6 months later so this is the third time I've had it and each time the symptoms are slightly different so it's hard to detect until it gets really bad, unless you have regular blood tests.  Stress or an infection can set it off again so I would advise you to monitor your health very carefully and find out exactly what has caused your thyroid issues.