Must admit this subject is now very very very boring!!!
Just do a search for mk4 hybrid and every single little piece of info will pop up, you just have to wade you way through it all.
As for turbo companies
CR turbo's do the hybrid treatment
Turbo Dynamics also do this service.
You will need an uprated clutch from anyone of the big companieson here, that is gonna be around £1000-£1300 fitted!!!!
Bigger brakes in reallity
As for mapping, several companies are more than happy to custom map it
RS tuning in leeds are the biggie on here, for a reason as well ;
Revo Stage 3 map ect...