I always let mine run to the end and politely decline offers received in the meantime. So far it has always paid off for me by quite a margin. Good luck
I think 1800 to 1 means they are probably fine!
If you get any time I think it would pay you to add some more detail to the advert - my questions would be to do with any maintenance or service history - maybe some more photos (inside etc) - plus are there any significant parts that might be better than people expect - eg tyre tread remaining, exhaust etc.
Also there is no "Yes" against V5 document which might imply you don't have a logbook which will worry some/many people. If you have got one I would definitely get the "Yes" in there.
Also its worth proposing a deposit to be paid in so many days and car to be collected and paid for within, say, seven days. This reduces the risk of you being messed about for very long.