London parties often have a entry cost which can reach £10 these days.
this money mostly pays for the security which are unfortunately required due to long standing problems with gangs with weapons.
There is no rules against “bringing something in”, but bear in mind that the cops aren’t stupid and may decide to do random stop checks at transport points. The East Anglia > Liverpool Street route is often watched by BTP/Metpol as a potential “drugs transit area”. Also whilst the Met may not stop the rave they do have a habit of stop checking anyone in the vicinity just to make it “look like they are doing something”.
Inside the venue, as expected in a large unregulated place you would have to also beware of getting ripped off.
