do you have to upgrade the brakes/suspension before attempting this kind of work? are there other downsides to having this done eg other parts components but under strain and wear out?
....Experienced professionals in the industry say that Volkswagen design and build an approximately +40% headroom tolerance.
The more you push the performance envelope, the more various components will be stressed if they are standard from VW factory. So it's a case of recognising that limitation and modifying accordingly.
Aftermarket brakes aren't necessary but as you're likely to be going faster at times you'll be glad to have them - Especially an improved pedal response feel.
Likewise, using your extra performance will benefit your handling and driving joy if your suspension is appropriately modified and it ain't a case of just slamming down low.