High estrogen can lead to breast tenderness, water retention, heavier periods (if you are having them) and headaches in some people.
Provera is much stronger than progesterone - it is literally progesterone on steroids - and provides robust endometrial protection so depending on your dose an increase may not be necessary - your specialist will be able to advise on this.
It can be challenging getting what you need on the NHS - I have to pay privately for my combined pill - however I made the decision to opt for the best treatment for me rather than take something less suitable just because it's free.
What I would say is find out what really works well for you, then look at what of that you can get on the NHS and potentially self fund the difference.
Alternatively don't overlook oral estradiol as an option if gel isn't getting you to where you need to be.
Oral estradiol is more stable than gel as it is absorbed more slowly through the gut so it doesn't peak as quickly.
The real world difference in clot risk is absolutely minuscule for healthy women without any risk factors, literally an extra 1 or 2 per 10,000.
It is sometimes easier to get a therapeutic dose of oral prescribed on the NHS as 2mg is considered a standard dose, and if you are self funding it's cheaper than transdermal.