Getting your greeting right in a sales scenario can make or break the deal before it even gets started.
Offline, you make a decision based on what you see, hear and 'feel' - as in 'gut feeling'.
That final point comes from experience - and you just can't teach experience. Anyhoo, back to the point.
Online the salutation has to be pre-determined ... coded into the email or web presence; so no seeing, hearing or gut feeling. However, you do have the organization's 'voice', that is, how the organization talks to its customers. This is based on a whole load of things, but mainly the organization's culture, ethos, brand values, the product/service it sells - and its prior relationship with the customer.
Given these issues, I just think that 'Dear Mr Charlesworth' is not right for an email selling holidays.
PS note how the content implies it is a leisure trip not a business trip. For business, 'Mr' might be OK.