Excellent advice indeed. It is not an insurmountable challenge to make a few day trips down to Karachi to look over potential cars. Perhaps a friend in Karachi can do the ground work for you. BTW, does it have to be a W115? you could also find a W123 in the same money?
W123, here is one for just 200,000. it is LHD though: #cd3ee459af
W115, This one looks Okish in the pictures, just 185,000: #cd3ee459af
W123, no A/C in this one and a bit rough but all that can be fixed: #cd3ee459af
All above cars are in Karachi, As you can see there are a few cars out there. You have to keep in mind that for sub 300k you will get a rough car. Important thing is to make sure it is complete and with minimal rust.