In the second reading of the Online Safety Bill, The Earl of Erroll suggested:

The first was on enforcement. This is always the big problem: how do you make them comply? One of the things that will work is the withdrawal of credit card facilities. If a Government or authority ask credit card companies to withdraw facilities from a company, they will, probably internationally. In fact, this happened not that long ago, a few months ago, to one of the big porn sites. It soon fell into line, so we know it works.

As far as I can tell this suggestion has not be integrated into the bill, but we'll see what the third reading consists of.

Signal, the encrypted messaging service, plans to defy the law and continue offering end to end encrypted services.

Note that this doesn't require any credit card processors to actually carry through, though it would require a credible report that they were asked to or otherwise faced pressure to. Specifically, if there are chilling effects (e.g. facing fines if they do not preemptively revoke credit card processing for non-complience), that would definitely count as pressure.