Sunnigirl, Please do no accept borderline, what your GP is doing is waiting for your TSH to rise above 10 which is madness, your low free t4 tells you that you need far more thyroxine(t4) in store. If you lived in Germany or USA then you would be diagnosed as Hypothyroid when your TSH goes above 3. The TSH can fluctuate and is not an accurate test but unfortunately this is what GP's and Endocrinologists go by
So, you need to ask for your thyroid antibodies to be tested along with your B12, ferritin, folate and vitamin D as deficiencies in these can give hypo like symptoms too. Many of us hypo's have deficiencies in these, do tell us the results.
Your GP will also ask for TSH and Free T4 and Free T3, unfortunately another problem that we all find is that the Free T3 is not tested unless an Endocrinologist has requested it.
You haven't mentioned your symptoms? Ideally you will feel better when your TSH is below 1 and your Free T4 is nearer to the top of your range, so 22.
Knowledge is power, read up as much as you can. thyroiduk.org