Yes, I have often use hotels for incalls just for a day at a time. For me, the best area is central London, but other ladies say it doesn't work well for them and they prefer other areas. I think there is no way if telling which area will be good for you until you actually suck it and see.

You could always ask potential clients for ideas on locations - I recently put a list of cities on my AW profile and asked guys to email me if they wanted to suggest a particular area. Obviously it's no guarantee that they would make a definite booking if you went to their town, but at least you'll get an idea if where you might get interest.