Re: Accurate Ads
This isn't a defense or critique of how the targeting works currently, just an explanation of the likely chain of events
Assuming you visited the bargain sites for the hotel in London, which I think you must have done to get the information that booking direct from the hotel was cheaper, then what happened is the bargain sites seeing that you were interested in booking a room at that specific hotel and being unable to see that you did convert on the hotel's own site.
Even pre-GDPR, that information wouldn't be shared between sites. Now it's illegal.
Similarly, the events and offers for around London would come from different sites/organisations, running into the same problem as above.