So if you were unlucky enough to need a replacement windscreen, would you get rid of the car afterwards ?

Thought not ....

No I probably would not. The OP is in a different position, he has not bought the car and the iffy screen would get on most peoples nerves especially if they had paid out big money. That is why he is asking the question He already has doubt

Its on the edge of the screen, so its possible air got in then was replaced by water, its difficult to tell by those photos, the screen surround afaia is not water tight as I think its clipped in place

the mark imo is not going to do any harm apart from aggravating the owner looking at it, but will be out of sight inside the car, the OPs best bet is get a windscreen fitter to look at it and get their opinion

Its on the edge of the screen, so its possible air got in then was replaced by water, its difficult to tell by those photos, the screen surround afaia is not water tight as I think its clipped in place

One hard frost and bang goes the screen!

Simple answer, if OP wants it, get the garage to replace windscreen due to risk of it breaking, or walk.

It may be worth the risk of buying and if the screen does crack and your insurance covers the screen get insurance to cover it,

Some insurances cover with a £75 excess depending on ins co and as long as you use their replacement service

So its no big deal having screen replaced if it does go, if your insured, any screen can break at any time its a risk on any car !