ur lookin at about 2-2.5k to get the 1.6 upto 140-150 bhp it would be more wise to spend a little bit extra and get a st170 lump put in for about 3-3.5k if u where addiment about keeping the car youve got.
but in all honesty u might aswell sell up and by a decent st170 for about 4.5k that way u will also be getting good breaks, suspension and that getrag 6 speed box