Why can't I see Live prices on shares I hold? (AIM)

Payment for order flow is not allowed in the UK though that’s a US specific thing.

That’s what I understand. But how will access to MM work? Will there be there no best execution price guarantee?

Im not well versed but I believe the Mifid II legislation forces best deal execution in the UK/Europe.

Edit: a quick Google this seems to explain it well

Yes, MM make their money though the spread, so not NBBO price.

Taking a look at FT which uses MMs

T212s

https://www.trading212.com/en/Best-Execution