I know they are vary in terms of size and power, but whats the regular size of a crime firm? Are they comparable to American crime families or Italian ones?
Also, I heard Liverpool has a very strong presence of drug organizations, so are these organizations basically some drug gangs? Or do they also focus on other businesses like gambling?
Last question: What kind of structure do they form with?
Thanks for anyone answering my questions.

It's impossible to give a clear answer, because like you already said they vary greatly in size and power but I can tell you one thing, I never heard of a firm with the size of any of the five families for instance, who have between a 100 and 200 soldiers and at least 500 associates.

About the structure.

One of the key concerns in the UK is the structure of organised crime groups and the extent to which they reflect or differ from the socio-geographically based mafia groups found in Italy and elsewhere. The picture of organised crime in the UK leans away from the traditional Mafia model towards conglomerations of career criminals who temporarily join with others to commit crimes until they are completed and then reform with others to commit new crimes.

Hollander nailed it really but you also have family based 'firms'. Firm is really a London thing though and not used so much the further north you go. In Scotland the only firm are the ugly sisters (Celtic & Rangers) and that's football not organised crime. There are loads of small gangs/mobs in Scotland and even more independents. I often see people say that Scotland is run by the Daniels mob or the McGoverns but that's just not true in reality. First post...

Liverpool tends to dominate the UK drugs trade and they have direct links to all the major players in cities around the UK.

Also quite a few major groups are families with only blood relatives being involved and trusted.

They dance on the Peruvian and spray the weeeed though.. famous for it la! But again very much the case. Ellesmere Port has a lot to answer for

Uk is a very small place

I can almost guarantee a London based firm is nothing like an LCn family in size

Smaller independent firms/gangs probably works better for them with less exposure and grasses.

There are some firms/gangs that have been in operation for decades without being decimated by the cops.

London is a huge city my friend, London Metro has a population of 14 million..