I don't think LP said is going to take 18 months to get an approval. The facility is GMP now. When the regulators ready they will visit Advent facility. This is beyond LP control. Who knows may be they already schedule to do that. I don't think NWBO is going to PR the regulator visit.
Can NWBO expedite the application for other RAs? Absolutely yes. They should not wait for MHRA approval.