From a purely economic perspective, buying immediately is not worthwhile compared to the 13 years of leasehold due to the tiny payment.
If you had the discipline to save the same amount you would have to pay for the property in an investment with a term until just before the leasehold contract ends, you would have something left in the end.
Mentally, the thought "what I have, I have" may be better; whether that corresponds to your personality, only you can know.
Personally, I would always choose the path that brings me the least stress and thus the highest quality of life – that’s why you buy/build.
Financially, buying later makes more sense.