On very limited data, LFDs are picking up positive Omicron cases slightly better than Delta, but they are imperfect. In particular we are relying in people doing the tests properly and if you aren't a regular user then a quick dip with the swab isn't going to always work. We can see fairly accurate LFD results from NHS workers since mostly (not always!) they use the LFDs correctly. That doesn't explain everything, some people just never show a postive LFD, it is a bit rough and ready as testing goes. Anyway in your case, doing a PCR sounds very sensible, so I would get yourself a PCR as you have arranged. You are up to date on your vaccines, so you have a good chance of being and remaining negative, but it's good to check before meeting someone who has multiple risks.