He, olgaga.. I know all these houses except the bungalow. I also know my area quite well... and taking these houses into consideration, I'd say our price is very reasonable!
Soo.. since I am getting all carried away here, I'll jsut type down something that probably no one will read. About the houses you mentioned:
The first one is the only one comparable to ours - and I can see it from our front window. 
It was on the market for the same price as ours is now, so I assume it has been sold for the price that is now mentioned. (Which would be an offer we might well accept, too...)
The house is not bigger than ours - check the room sizes.
The back garden is not bigger than ours either - only tidier, so they have more of it on the pic. Their front garden is almost non existent, whereas ours is massive. I consider their decoration to be very outdated... but that may be a matter of taste. The only thing they have that we don't is parking on site... and that may be their big selling point.
But they sold very quickly, so that makes me more hopeful for ours.
The other houses you showed: The 4 bed is a mid-terrace, it is in Newlyn, which is not Penzance, and it has no real garden. (courtyard garden is more like a path!) And it 'needs updating'. It is very close to the sea, but has no view of it, while still being at risk of flooding when the weather is wild, and it's on a noisy busy road.
Parc Wartha crescent requires updating and has lots of road noise.
The three cheaper houses are all mid terrace and they are tiny, with no gardens.
The Gwavas house has such lovely views because it is on a VERY steep hill. It is also in Newlyn, so not in Penzance, it's on a very rough estate (although in their defence they have been improving), and it needs updating.
That sold house on the seafront is smaller than ours, with mini garden, and has sold for 'offers over' 150000, which was apparently 'priced to sell'.
That bungalow is the only one I have not ever seen... but it says needs updating, it is again in Newlyn and can apparently only be reached via a foot path?
You missed this house: www.rightmove.co.uk/property-for-sale/property-15535983.html?premiumA=true
Is around the corner of ours, admittedly nicer than ours, and not selling. But I had a look at it the other day, and, well... I think their neighbours may be the problem...
I've done my market research, really, I have!