Niamh, welcome to MM!
I also visited Professor Studd and he prescribed exactly the same medication for me although I have since reduced my Oestrogel dose to one pump every 12 hours.
Like yourself, I am intolerant to all synthetic progestins and to a lesser extent Utrogestan which, as you probably know, is a bio identical progesterone and much more like the one we produce ourselves. I always take it vaginally and there are fewer side effects (like breast pain) when you take it this way. When taken vaginally, you are more likely to tolerate it and yes, it is stronger (probably about 50%) because most of it reaches the womb and does not get lost in your digestive system so you can get away with using 100mg for 7 days per month. If you can, try to find an applicator and place the capsule right up to the cervix, you don't need to pierce it though.
There is no reason why Utrogestan cannot be licensed to be used vaginally in the UK, it is virtually everywhere else. My gynaecologist (not Professor Studd) thinks it should be always be used vaginally.