Having worked for years as a police officer in London and Manchester I have yet to even hear of a no go area let alone avoid one .
Behave
I know of an incident in Thames Valley. Horse trailer stolen, with the postcode in 24" letters on roof. Owner suspects it's in a local-ish traveller's site, so asks friend with PPL(H) to check it out. Confirmed, so the owner tells the Police. Police tell him to claim on insurance, as they won't enter the site for a £3,000 trailer.