If I was you I would avoid the girls who tour in and out of a Merthyr, they are all run by the same pimp and are £90 for 30 mins and £120 for the hour. Services are not as listed and there are some seriously crazy girls in the group.
They occasionally tour and stay in a hotel in the town centre, they move on because they are like the only ice cream shop at the seaside to start with but when punters visit they soon realise no body will return because of the shit taste.
Cardiff is your best bet.