This was in fact Rik Mayall's second final movie role before dying suddenly of a heart attack at his home on 9th June 2014.
While running the offline edit, the director of photography (Nicholas Peel) copied a section of the film to an old VHS format, then proceeded to degrade the tape by crumpling it up & stepping on it, then re-capturing the damaged video to give it the distinctive lo-fi look.
The Cafe, the main location was at the time a working cafés; "The Grand Baguette". The producers arranged to shoot in the location during nights & weekends when the cafés was closed for business. While the cafés's owners were also hired to provide the films catering. As a result the cast & crew grew very fond of the cafés's milkshakes & would return frequently once the shoot was over to have more.
The cafe location was a real business, & as such all the fridges in the shop were on during takes. This lead to dialog recordings that were very noisy, so the sound editor had to spend much of the post production time removing fridge noise & restoring the recordings to a quality that was usable in the in the final mix.
While running the sound edit, the sound designer (Simon Norman) liked the sound of the degraded VHS effect made by the offline editor, but it was done without final edited dialog recordings & was unusable. So the sound designer had to re-sync all the dialog rushes & rebuild the degraded sound from scratch with final dialog & completed sound design elements added in.