I don't know how the business model works for HOD and how many mouths they have to feed but renting 2 x 2 bedroom flats in Victoria is going to cost over £5,000 a month, say £200 a day.
So if demand is strong and they have 5 girls working each day at £130 per hour, booked for 5 hours each and are taking 40% commission they are making £1,300 minus £200 rent minus other expenses say £100 per day, so £1,000 per day, £30,000 a month, not bad. Increasing to £150 an hour and maintaining margin gives the house £200 a day extra, that's marginal and the bad feeling caused by the price hike might even make them lose out.
Seems niggardly unless the intention is to increase quality, or maybe it's being driven by the girls who believe they are worth more. Got to admit shagging 5 punters a day in a brothel for under £500 doesn't sound massively appealing when you can go solo, charge more and keep it all.