Sure you're all aware of this already so apologies for stating the obvious, but the Czech girls at Masshouse usually offer threesomes and even foursomes.They are very reasonably priced , all well rated escorts , presumably experienced with threesomes and all in the same incall location to start with ; saving a lot of hassle and additional expense.
Blond Lia is on holiday at the moment , not sure about the others , but this seems to tick all the boxes for a first venture into the field.