Lots of men pay women for money in lots of ways- some do it outright and procure a lady of the night and pay them cash, some get a girlfirend and suffer endless requests for gifts and boring venutres out if they are high maintenence and some get married and have to have a new kitchen fitted every 3 years
when colours change and it's no longer fashionable ;-)
There is nothing any more seedy or odd in having sex with a prostitute than any other woman and as he's single and not your partner it's really not your concern, but reinterating what the others have said he really doens't need to go to London to find one, they are everywhere and generally don't look at all the way you'd imagine, your neighbour might be one, you'd never ever know.