London is the best punting area in UK. I sometimes read the other regions threads and reviews in UKP and the members who post there need to drive miles to find a decent WG.
In London you have probably thousands to choose from and unfortunately the ones who can really DT are only few, even less can do a facefuck.
If you restrict your criteria only in central London (as central I think you mean zone 1 because Canary Wharf where Suzy is based is quiet close to the centre), you are maybe too demanding.
The only thing I can advise you is to do your research in AW for area, DT and submission and directly ask to the prossie if she is able to FF for the time you wish. Aspect also to pay extra for that.
If you are worried about the risk to waste your money, ask for a short session with the possibility of extend.
15/30 mins, if you are happy with the service provided you pay more and stay, if you are not you leave.