HI Flo12
I'm a bit confused. If you are taking Elleste Duet then finish the pack if you can but if you haven't started the combi pills with the progestogen in them you could take utrogestan instead for the second half of the month as you suggest. However you would need to take it with the Elleste oestrogen only tabs not the combi ones - if you have another pack that you can start? Or you could just switch straight over to the gel and utro (and stop the Elleste completely)- as it's the second half of your cycle?
How much Sandrena have you been prescribed? You might find if you've been given the 1 mg sachets that this isn't enough (compared to the 2 mg oestrogen in the Elleste) but see how you get on.
Yes you're quite right you should be taking utrogestan cyclically if you are peri-menopausal still - ie 12 days per cycle. You may well find you are less sensitive to the Utrogestan than the norethisterone tablets - but there is always the option of taking it vaginally (off licence) if you do react badly to it.
The Vagifem pessaries are very low dose oestrogen and will not put you at amny oncreased danger of womb cancer - it is the HRT which needs to be at the correct dose - specificially the right amount of progesterone to protect your womb lining and if you start with the licensed dose that's the best idea to see how you feel and how your bleed is on this regime. Vagifem is a long term vaginal oestrogen so you will need more once you have finished the first lot. You use it daily for a fortnight then at least twice a week thereafter.
Hope things work out OK for you, and do let us know
Hurdity x