I recently tried chemical leak sealers in my Freelander 1.8 K series cooling system as I figured it would help eliminate leaks from the cylinder head gasket area which affected my vehicle. In reality, the chemical sealer did stop the leaks, but what it done it blocked the tiny pencil-diameter type coolant passages of the cylinder head, which lead to overheating. Over time, the chemical sealant holding back the leaks eventually dislodged under high pressure and the leaks started again. I wouldn't recommend chemical leak sealer on the 1.8 K series Freelander for the same issue I had, I would recommend you simply fix it and fix it correctly by renewing the oil rail at the same time when you do this job.

Here the video on the blocked coolant passageways on the cylinder head.

Leak Sealer blockage of Cylinder Head 1.8K Freelander - YouTube