IIRC , (although apparently recently hung up her stilettos) Mia in Shoreditch was a forum darling and one such SP, who had an all inclusive policy. No forum kudos or likes needed for that one, but happy to receive your adulation 
The point about extras is simply a case of mathematics. You factor in all costs and reach the price of what you want from a punt. It's the total price you pay that's relevant, not the breakdown of costs.
And for the mathematically or statistically challenged, one should consider the percentage of a particular nationality across the total of SP's available. I suspect that Brazilian, Thai and Romanian would account for the vast majority. You only mentioned Brazilians, but my experience is that pretty much all the other nationalities are also charging for extras far various services.
Therefore, it must follow that the vast majority of providers, of all nationalities, will be asking for extras.
You can of course "set me straight " with some additional reporting 
Mia was not your typical latter-day Brazilian SP in London, so her market approach was not born of the traffickers from Brazil:
She was born in Brazil, but grew up in Britain she said. Her accent was soft and hard to place, definitely not a "Landaahn" accent though. Her feminine, submissive voice over the phone was enough to get me ready for the next 90+ minutes.
Charging extras has indeed been around a long time and found non-uniformly in use by all manner of
individually-minded "escort" since well before the flood of "Brazilians". That is not the point and you know it. Anyone familiar with the walk-up scene in Soho and perhaps most any other UK RLD will have found the atomised pricing on a menu of services par for the course for decades. The "escort" scene had for at least the last couple of decades been dominated by a base offering that included more than begrudging sex, restricted OW and maybe a few pecks of the lips for the base fee and the few extras charged were
not your typical vanilla GFE fare e.g. CIM, CIF, swallow, WS, A, snowballing.
It's not just mathematics it's about value for money, the mileage you get or don't in the case of these (not so) micro-payment grifters, disposable income and the likely earnings of your customer demographic. 100 or 150 quid is still a lot of money even if it buys less essentials than 5 or 10 years ago. Earn that as your hourly rate as a non-sex worker and you're on 180+k pa for a 35 hr week. An SP on just 5 1hr bookings a day for 5 days a week is still on 130k pa equivalent. Sure there's a bunch of punters here on well over 100kpa equivalent (working or retired) but I'd be very surprised if they're the majority of UKPers or the wider pop of Johns.
Reading the reports from those who've mongered in Brazil and other LatAm nations it seems to be that SPs there are more inclusive of their offerings (at far cheaper prices for longer). So it doesn't seem to be so much an imported "cultural" practice as a sharp practice implemented for the UK market. Similarly the reports I've seen of the waystation markets of Spain and Portugal also seem more inclusive (and cheaper). Happy to be corrected by those who have the more detailed recent and historical perspective on any/all these places.
The preponderance of Brazilians and their LatAm brethren that are shipped in with them are dominating the "affordable" end of the market here to the point that recent Thai SPs are beginning to implement the practice (no drogues...) at odds with the established Thai agencies and pretty much all their sisters back in the fleshpots of Thailand.
After my earlier post I ran a bunch of <=150ph (nominal price) London searches on AW just changing nationality each time for each of the LatAm countries to see if any buck the trend. Of the some 400+ Latina SPs less than 5% were reported to have offered more inclusive pricing (and some of those are just higher base prices), all others seemed to be "esstra" girls. c.1200 SPs in London under 55yo; 96 Poles, 42 Thais, 190 Roms, 167 Brits, 140 Hungarians, 20 Ukrainians, 9 Russians, 20 Chinese,
338 Brazilians, 32 Colombians, 9 "Spanish", 7 "Portuguese", 14 Dominican, c25 other LatAm. Look for <=200ph and you get 1734 SPs nearly +300 Brits, +26 Roms, +25 Poles and +120 Brazilians and not alot more from any other nation (a few more LatAm).
The statistical argument is spurious because we're talking almost entirely about how this affects the cheaper/non-premium escort market sub 200ph. Just one let alone multiple extras at 20-30 each is ludicrous whether starting from 60, 80, 100, 120 for 30 mins that only grants sex, OW and lip kissing until you pop just the once. Take a Brazilian for an hour's spin with OWO, 69, (D)FK and you're at 160-220ph without the saucier trimmings offered by others starting at less.
