I have a similar situation. I've applied to 4 med schools... interview at one (Leeds), rejected by 1 (Cardiff) and still waiting for the other 2. My problem is, one of the other 2 I'm waiting on (BSMS) put me on an interview reserve list... due to personal reasons/commitments BSMS were to be my firm had they made me an offer... but because I'm on a reserve list I can't choose a firm/insurance once all my other decisions have come through unless I withdraw but I can't withdraw because of my personal reasons. I explained everything to them in a message on their platform and waiting for a response. A condition they made was that if I didn't get any other offers, I'd get first choice from then in clearing... that would mean IF I got an offer from e.g. Leeds, I would potentially have to decline it.
It's a really crap situation to be in.