As Naughtyboy says, for £150/HR your best bet is the Asian agencies, who have a number of girls in the area. Bayswater and Edgeware Road are only one stop away on the tube from Paddington. Do your research on here for the good ones (Tracy, Anna, etc) and the ones to avoid. But be aware that the girls book up fast, particularly for the kind of time you would be looking for, so you will need to book in advance - probably the day before if not earlier.
I suppose it all comes down to how certain you are what time your work commitment will end, and how important it is that you catch your train. If your tickets are not valid on a later train, it could become very expensive for you if you miss it.