Yeah, I know what you mean. Some of it was over MY head too!
I think you have analyzed the issues correctly: potential range versus cost and compatibility. There is no easy answer. Consider that asking if a 449 MHz radio with a licence would be better than a 446 MHz radio without a licence in the U.K. is identical to us folks asking in these forums from North America what is better: GMRS or FRS.
In some ways, you have more choices than we do: we are not allowed to use FRS for business use; your PMR446 radios can be used for business or personal use. In the U.S., only the licence holder or their immediate family can use GMRS radios, meaning that if a photographer wanted to use it for their business, each person in the business would need their own licence. Your PMR 449 MHz radios use instead what is called a “Simple UK” Business Radio Licence.
You also have industrial-grade choices such as the Motorola XTNiD PMR446 and the Mitex licenced PMR 449 that are considered “business-class” radios that we don’t get here and are built to much higher standards than our consumer-class FRS or GMRS radios. (There are very few military-spec industrial-grade FRS/GMRS radios available for sale in North America. One reason is that the cost of the radio plus the cost of the $80 GMRS licence adds up.)
(Dealers such as buytwowayradios can take many business-class industrial-grade radios and program them to GMRS frequencies though.)
So, as I said, there is no easy answer. Can you rent a couple of business-quality PMR446 and a couple of licenced PMR 449 radios to compare?
Have you thought about simply renting business radios every time you need them? (You don’t need to worry about any licencing; you simply turn them on, turn them off and charge as required. The renting dealer is the one that has the licence required.)
Have you talked to a good two-way radio dealer in the U.K.?