Unfortunately, your assumptions are correct. You will not be able to sell in EU until you certify your products to MDR (not only the audit, but submission of MDR-complant device file as one of first steps). To sell in UK, you need either CE or UKCA certificate - which can only be issued by 4 NBs (currently), all of them are overbooked.
Did you submit your MDR application? When, which NB?