People Just Do Nothing: How BBC3's latest comedy started with a series of YouTube webisodes

People Just Do Nothing (PJDN), which returns on Wednesday for a second series on BBC3, is a mockumentary about Kurupt FM – a fictional pirate radio station playing old-school garage – and the responsibilities and irresponsibilities of the characters who run it. They are Grindah (its proud but irritable head honcho), Beats (a DJ and stepfather to an obese videogame fanatic), Steves (a drug-muddled man-child), Fantasy (a ladies' man of few words), Decoy (a remixer who, unbeknownst to Grindah, fathered his daughter), and Chabuddy G (an Asian Del Boy).

PJDN originated on YouTube in 2010 in a series of webisodes made by a group of friends who poked fun at their own youthful interests. After coming to the attention of Ash Atalla (executive producer of The Office) they developed a first series, which was initially shown on iPlayer. They were then paid by Roughcut TV to develop a second series before it was commissioned. By now they have something of a hefty cult following and are on the verge of making a popular success for the BBC.

"Stampeding through your settlement, like a storm of angry elephant. 108.9, straight for your mind. Like it or lump it, basically," freestyles Allan Mustafa as Grindah. In Chesterton Court, a boarded-up block of 1960s flats, on west London's notorious South Acton estate (previously seen in Only Fools and Horses), the PJDN team are filming their final scenes in the flat they've used for two series as the secret location of Kurupt FM. After this, the entire estate will be demolished and redeveloped.

Mustafa and Hugo Chegwin (as Beats), who once worked together in a call-centre, begin improvising a scene in which, during a "weed drought", they praise the merits of a "skud zoot" rolled from settee-sweepings of assorted skunk strains. "It smells like burned hair," notes Beats. "Even better," splutters Grindah. Later Chegwin will improvise for an hour about euthanising old folk and how radio was invented in 1898, "back in the Game of Thrones era, to broadcast warnings about dragons".

Director Jack Clough is planning to "grab footage" of the demolition of the flat for possible use at the beginning of a future (third) series. "We could recreate the flat in a TV studio next series – and could have done that to begin with," notes Clough, "but the boys say that wouldn't feel right – they're sticklers for mood and detail and realism." PJDN is, at heart, a comic homage to outer-west London, and especially Brentford, where Chegwin and chief writer Steve Stamp were raised, on the Haverfield estate.

"We write about a half-imagined world that we grew up in," says Stamp, who studied English literature and film studies at Sussex University. "Our characters sort of got stuck in a time period and continue to chase their dreams and stubbornly refuse to adapt – to grow up, basically."

"A lot the people we give shout-outs to on the microphone – like Alfie Danger, Nathan B and Johnny the Little Mincer – are people we grew up with," says Mustafa, who was raised in New Malden. Now 29 and living in Chessington, he satirises and celebrates the years – between the ages of 15 and 19 – when, "prior to liking hip-hop and Europe-y things", he was devoted to garage and appeared on Kingston's Rampage FM.

"But I think I was always good with rhymes, to be honest," says Mustafa. "At 11 I bought Doggystyle and I'd emulate Snoop, spitting his bars and playing around with them. At school I'd do impressions of Romeo from So Solid. I find it quite natural to freestyle random shit."

Asim Chaudhry, who camcordered and edited the original webisodes, plays Chabuddy G. "We love delusional characters," says Chaudhry. "Chabuddy is inspired by my mates who have Polish wives and Poli-stani children and my uncles in Hounslow. And especially my dad."

"Dad is a trier and always had different businesses but could never hang on to money. He had an Italian restaurant with Indian chefs so the risotto tasted of biryani. He had a calling‑card business based in Germany and a big meat-storage freezer in Pakistan which broke down so it cost him £20,000 in meat. Like Chabuddy, Dad had an internet café and worked in a Portakabin."

"They're totally self-aware and they know each other so well," says series producer Jon Petrie. "They travelled around Thailand together and do impressions for each other. It was a bit of a challenge because none of them had done TV before. But the BBC has interfered very little."

The team are sitting on a park wall next to some freshly sprayed "Kurupt" graffiti. Grindah scoffs at the BBC crew for wearing "climbing gear" (North Face clothing). Today he, Beats, Steves, Decoy and Fantasy, with much attention to detail, wear an array of classic gear – Kappa, Tacchini casual, 1990s Air Max, Reebok Workout, Ralph Lauren polo caps.

After a spontaneous bit of filming in front of a mural of Nelson Mandela ("from Jamaica") en route back to the Kurupt flat, they mix and MC over their own music for two hours, while smoking prop (theatrical) weed and developing scenes of lyrical excitement, interrupted by Beats' phone calls about a lost key or unwashed pants.

They list their comic influences as The Office, Spinal Tap, Alan Partridge, Ali G, Laurel and Hardy, and, increasingly, Mike Leigh. "We never really wanted to be actors or care about acquiring celebrity," says Mustafa. "Our passion basically is for the comedy."

'People Just Do Nothing' is on BBC3 tomorrow