to above, have you tried st marks st / st marks rd? thats the road between montague burton and leodis, st marks st being the one with st marks halls on the left. that road is good for parking, but not after 730. Theres usually spaces on st marks rd (turning right at the bottom of the hill), although this can involve a further 10 minute walk to uni up a very steep hill. Also I've seen a fair few car windows smashed round there, so dont leave your car too late.
That's where I always head if I need to drive into the uni.