Agree the risk is generally very low. And if there is a raid, as long as the brothel lass you punt is not coerced & not underage, and you don't give any false info to the police if they question you, then you're just as legally safe as with an independent. It's the brothel operator that's at risk (Im not a lawyer, but fairly sure this is correct.)
Like you say a true independent is the safest. I'd say a well established brothel or agency booking may be safer than a TOFTT type booking than with AW or viva street - those may be independents, but they also may be pop up brothels where there's coercion going on, and in the eyes of the law that sort of punt counts as rape.
As to the chance of your brothel being raided, it's going to depend on the local authorities in question, so google searching for news of raids for the brothel or in its locality might help.
I dabble in politics a bit so know for a fact that some Councillors are cool about the established brothels- they pay at least some business taxes, they keep demand away from the pop up brothels, and they even (arguably) do some public good.
On the other hand you obviously have some areas where councillors, officials & senior police are White Knights happy to do the bidding of feminist pressure groups. Or in some cases there might be a suspicion of involvement with more serious forms of crime. Hence always a risk of raids in some areas...
