clifford alarms are quite good just look for thatcham category 1 approval and se what fits your budget.
What gti you got cos it varied from year to year for the electric windows, e.g. 8v not standard but some have them factory fitted as special editions, i think all 16v were standard apart form really early ones but im not entirely sure, late ones should have them, (g,h,j,k plates)
welcome by the way
ed