There is a post-op niche, but it is significantly smaller than the pre-op one.
Whichever option you pick, you should know - if you don't already - that the transphobia on the generic 'punting' review sites and message boards can be absolutely rabid.
If you're out, the review sites won't accept reviews, nor the boards ads, but if you go 'undercover', you risk clients speculating about you there on the basis of your voice, hands, neck, eyes etc etc.
Particularly if you're in / near London, it's worth getting in touch with the SW5 sex work project (020 7370 0406). They are in the middle of some major changes but at least some of the work with trans workers should survive even though I'm not sure what services will be on offer.