If you have the head for it, I would probably do both at the same time. Keep trying, and get on the books of the rmc clinic.
A lot of what they do is mopping up after the fact - once you’ve had a certain amount of mc they will test the remains of the baby for genetic issues. They will test you for clotting twice over a two month period. They should scan your womb for any irregularities, bumps, reasons why a fertilised egg isn’t sticking. Possibly offer you a hysterescopy. Possibly do a procedure where they put dye into your Fallopian tubes to see if anything is remiss there (I think it’s called a HCG).
They should discuss options with you regarding progesterone. I believe this really worked for me, but there are dividing opinions. And I feel like you could be at the mercy of whatever the opinion of the doc in charge is.
The reality of finding a cause is unlikely. And imo this is why you should keep trying. Secondary infertility is really confusing, and it’s really hard when no one can give you a straight answer. Be prepared for that.
Regular scans you can do via self referral at the EPU as pp says. And as another poster says, once you are pregnant you remain under the clinic’s care and this is very reassuring. That’s what I experienced at Tommy’s, although most of my rmc care was elsewhere.
In case it helps you to know, I had very regular cycles, and for me it was a question of how late my eggs are released… they often fertilised, but had only a couple of days before my womb lining started shedding for my period. This is where I think the progesterone helped.
When we went for private ivf, when it came to transfer, I was scanned every couple of days. This is when it became apparent that my body was not dropping the egg at the optimum time. Turns out my first DC was a “miracle” lol. A little clingon, which all makes sense. As it took a couple of weeks to show up as pregnant on tests, and his EDD was eventually moved two weeks later.
The NHS offered to scan my cycles and I said yes… twice… but it never happened. My consultant thought we should be trying naturally, and wasn’t really keen. And I think it’s a case of resources.
Sorry for all the info. I wish I had had more info when we were right in the thick of it.
All this to say that I wouldn’t stop trying, if you and your partner and your DC are in the right frame of mind. And def get into a clinic for the tests/discussion/support.