If it doesnt have isofix, you can simply buy the brackets from the main dealer and instlal them.
I did that on my B5.
ISOFIX is waay better than the seatbelt anyway so i'd recommend this even if the seatbelts did work.
My mum takes the wee one out once a week and doesnt have isofix, and the seatbelt fitting is really awkward compared with the isofix seats in our cars.