Oh they are difficult to find and yes it takes time. For me, typically 2- 3 months or so. That is in part because i am am fussy on the type of lady ( i like slim or petite, no fake boobs, no filled lips, no big ass) and who wants to and is actually avaialble to do the things i want to do together. Many say they want to travel with you but actaully aren't avaialble to do so. But its also because as you say CroPunter many now have a PPM mindset and i don't do PPM's (on the basis that if they are PPMing you, they are probably PPMing many others too.
I usually do 2 or 3 platonic "dates" (unpaid) first to test the "connection" and ensure we click and like/want the same things before making an arrangement - obviuosly some things need to be discussed and agreed including how often we will meet - ie twice a month or 4 times a month etc and the sort of things we do. I do 3 or 4 times a month and usually overnight at my place - unless we are away on a trip, or city break etc.
it is bloody hard to find these ladies now, but its still possible. I have had 4 long term arrangement over the last 4 years or so and with 3 of them i knew in advance when it would come to an end - because of her visa, or leaving University etc so was able to plan ahead and look for the next one in plenty of time. I am now on number 5 and about 4 months in. But maybe i should add that number 4 and number 5 are not London based as i don't come to London so much these days - but i still get a fair number of London ladies contacting me when i am looking. (my account is deactivated when i am not looking)
so keep looking and maybe try just "dating" a few - meal and chat only, no pay/allowance/PPM and no sex. I make that clear - a few ladies want paying for a platonic meet and i just politely decline those but some also want a "proper connection" and are happy to invest an hour or two of their time, especially if they are getting taken to a nice restaurant. its hard work but it work for me! Good luck!