Lost - so sorry you find yourself here and for your heartwrenching losses but welcome and hope we can help.
I would say if you have had two mmc and a hx of endometriosis (which some consider immune related) then if you could have the immune tests first then it would be worth it. It might avoid ivf altogether or prevent you wasting you frosties if there is an issue.
If funds are tight an option would be Prof Quenby at coventry who does the uterine biopsy for natural killers for about 400 as its part of a research project. However i think as far as immune tx goes she only really does steriods whereas dr s will test alot more things (expect to spend about 2000) and has alot of treatment options which many people on here have been sucessful with.
Have a read of the repro immunology bible - 'Is your body baby friendly' by Dr Beer. There is a list of conditions/health probs and fertility/pregnancy problems that if you have he advises an immune work up.
I have been trying for no 2 for over 2.5 years now (no 1 took 18mns) but i went to dr s after my first miscarriage as i struggle so much to fall preg that i could nt bear to lose another if i got preg to something that could be treated.
I hope that helps, i m sure others will chip in, especially hopefully Trying who is doing ivf with immune at argc right now.
Take care and lots of hugs. x