Hi Lesley, I was in the same position as you two months ago although my lining measured 33mm. I was referred for a hystercopy under the two week referral. This confirmed the lining was indeed grossly thickened and not smooth, they took a biopsy and fitted a Mirena coil which I wasn't sure about, I have never taken hormone tablets and I'm not keen on any form of medication, but they said that this would protect my lining from cancer and work to thin the lining. The following week I had the results of the biopsy which was simple cystic endometrial hyperplasia, with no abnormal cells.  Coil seems to be working as bleeding substantially reduced, but need to give it six months to see what it can do. Will go back for another check up and biopsy in six months, will then be monitored but hope that the coil will do its work.  I think my body was just not producing enough progesterone and I am happy that the coil is providing this directly to the right area without having to take pills.  It is a worrying time but I hope that you get this sorted.