On reflection, I have some more to add. The following thoughts apply to my experiences with 'massage' places rather than WGs from AW (although they sometimes overlap).
Although I mentioned that sometimes the masseur is in rather a hurry, or unskilled, you're not a passive party here. Depending on the location, you may need to be clear with the person that you would like a happy ending - some massage places like to keep a low profile; some will expect it. However, you will need to set expectations that you might need a bit longer than they ordinarily expect. You will also need to be direct with them about how to touch you - usually they'll be in a rush, and think that frenetic wanking is the way to go. Tell them you want a very slow, very teasing build-up. Also tell them (even if it isn't true) that you're not goal-oriented, and that she should take her time, and concentrate on keeping you hard, rather than getting it over with. This can have the added benefit of avoiding the dreadfully off-putting habit some people have of glancing at the clock, or urging you to come. If you take the pressure off them and yourself to perform, you're more likely to be relaxed, and enjoy yourself, and you're more likely to reach a satisfactory conclusion. In all respects, remember - you're the one paying for the service - it's up to you to guide them. Most ladies rise to the challenge, and have a wide range of tricks. If you find someone you like, and build up some rapport, this can be even better.
Two places where you're certain to get 'extras', and where, if you're clear, and can get past the occasional language barrier, you can explain what you want and how you want is are the asian massages places on London Road, Fratton, and by the station in Havant. Both frequented by Chinese ladies. The Fratton place has more variety.
Mods: feel free to remove this line if you feel it's inappropriate: You might find support and like minded people on the auto-censored (use a search engine), which is devoted more to the sensual massage side of things than out and out sex.
Good luck, and be sure to share your experiences.