Strickly speaking I don't think there's too much difference between doing outcalls only, I never used to use hotels and had plenty of bookings - that, of course, was a different financial climate though.
I still get a lot of outcall bookings sometimes and, for example, last sunday I booked a hotel and yet was out all day doing outcalls and had one half hour incall at the hotel.
Getting a hotel even one day a week is a good thing though, keep up on your website/adultwork what your incall day is and if anyone phones for one just let them know the day. If you don't have appointments, don't book - last minute is good for booking the morning of.
If you're in London I can send you a list of what some of the topsecret ones are (think i've stayed in about 11 of those).
xxx