Hi Jane, that is good that they are still checking. Do you know what they will test? Be sure to see all the results yourself. I hope they will do all three or four thyroid tests: freeT4, freeT3 as well as TSH. If the TSH is higher than 3, it's definite problem.
The video was to show you the far reaching effects of low thyroid. It affects every cell in your body. Clark has a series of 24 videos which point out other possibilities such as adrenal dysfunction, vitamin/mineral deficiencies or other causes. The problem being that slow metabolism will result in slow digestion.
It's important to break down nutrients to have the stomach working well with enough acid to demineralize important minerals and other nutrients.
I hope the doctors will also check some of those nutrients since they are important in using the thyroid hormone in the way it should be used. Iron, folate, ferritin and folate along with vitamin D should be well in the ranges and ferritin over the halfway mark. Be persistent, I'm getting the feeling that NHS doctors do not feel they owe you anything since you don't pay for office visits. I'm in the U.S. and have not experienced it myself but reading so many deflating posts have me worried about people in the UK.