Amongst the things I'm not is an immigration lawyer
Having said that, the Home Office's website <
http://www.bia.homeoffice.gov.uk/> has been very good when I've needed to know the details of what's ok with various visas for people from various countries.
You may find that you can work only if you're
employed by someone, rather than self-employed (which is what practically all escorts are).
If so, you would be working illegally. You may or may not get thrown out of the country if caught, but would certainly have problems visiting here again.
It sounds as if you would be fine with taking this risk, given the comments about tax. Just be aware that the tax authorities do take an interest in ads from people they don't know are paying them money.