Just replied to your other comment, before I saw this post.
GPs shouldn't manage Graves, you need an Endo, and I think your GP has demonstrated perfectly how incompetent and incapable he is of managing this condition. Grave's needs careful monitoring, Carbimazole is a strong drug and if you stayed on the same dose for a year with no monitoring and no titration goodness knows what state you'd be in.
This is the NICE guidelines on Management:
"How should I manage someone with overt hyperthyroidism?
Admit people with severe symptoms and signs of hyperthyroidism (for example fever, agitation, heart failure, confusion, or coma).
Refer all other people for specialist management. The urgency of the referral will depend on clinical judgement."
Just to be clear, when diagnosed with hyperthyroidism you're either admitted to hospital or you're referred to a Specialist, there isn't an option called "GP just wings it". If you read on, they are allowed to start treatment whilst waiting for the referral to come through, BUT they should only prescribe Carbimazole if they've sought Specialist advice.
This is what the NICE guidelines say about Monitoring:
"How should I monitor a person on carbimazole or propylthiouracil?
Ensure regular monitoring of free thyroxine (FT4) and thyroid-stimulating hormone (TSH) during and after treatment with carbimazole or propylthiouracil to guide secondary care adjustments to treatment and avoid iatrogenic hypothyroidism. Monitoring may be carried out in primary or secondary care.
Monitoring of titration regimen:
Initiation of carbimazole or propylthiouracil: monitor thyroid function every 4–6 weeks for the first few months.
Maintenance: less frequent monitoring is required (approximately every 3 months).
Dose reduction should be considered when the FT4 concentration falls to low-normal or below the normal range, or the serum TSH concentration increases (indicating development of hypothyroidism). Drug dose should be titrated against the free triiodothyronine (FT3) concentration in cases of triiodothyronine (T3) toxicosis.
Persistent TSH suppression should not prompt an increase in carbimazole or propylthiouracil dose."
Ask to be referred to an Endo immediately, I don't even understand how you've been diagnosed with Graves without seeing an Endo (I had an uptake scan). In the meantime, get copies of all your blood test results so that you can see whether or not you've gone hypo, and perhaps draw your GPs attention (and the practice manager) to the NICE guidelines.