i'd just buy the exhaust system and chuck a cam in..there is no point in spending ages fitting an 8v head with only little return..the exhaust system and cam is a piece of cake and power increases will be seen..imo if you want to go a lot lot faster, you need a bigger motor, end of story.. you could spend hours and hours on a 1.6 for say 3-6hp but what's the point!? do the easy power gains for now and when you can afford insurance/car etc then spend the time and money more wisely, on say a 2ltr 16v 150hp abf engine and slap that in your mk2..you'll be laughin with oh lets say around 175hp per tonne with that beast lol!
Just thought id reiterate this is only my opinion, dnt take it to heart.
hope this helps you in your quest for speed!