I hope nobody minds my registering just to pop my head in to add to this topic. I developed an extension for chrome to help with just this process by pulling in relevant data from the Land Registry and displaying it in an easy to interpret format.
As well as showing you the previous sales of the property, and others in the same street, it will give you a rough estimate of the current value by doing the same calculations as the land registry price calculator - it does this not just for the last sale, but also the previous sales, and will do the same for the other addresses too.
Looking at the listing with the extension installed, I can see the £157k valuation just by opening up the pop-up window. But I can also see that it is valued at £128k based on just the 2001 sale price of £76k. By switching to the addresses of the other houses, I can see that the valuations based on their previous sale prices all come in at about £110-143k, adding weight to the notion that the asking price is over the top.
No. 54 sold for £128k last march (giving it a current value of £131k), and 59 sold for £142k in october giving it a current value of £144k. Nos. 44 and 61 both have two previous sales, and the 2nd sale of both were within 5% of the valuation that the price calculator gives based on the sale price before. However, the 2011 price of this house was 23% above that value, suggesting that the current owners we're a bit gung-ho in paying £150k.
The extension also tells me that the council tax record for the property does not have an improvement indicator on it (or rather doesn't tell me - it will flag it up if it *is* there) suggesting that there hasn't been any significant renovations (none involving planning permission and considered by the council as potentially increasing the value of the house).
And, it also tells me that when the house sold in 2001 for £76k, that was about average for a semi-detached in the area - but when it sold in 2011 for £150k, that was a fair bit above the average price of a semi detached in the area, again suggesting they may have paid more than they should have done in hindsight (i.e. £150k for a house that is statistically still only worth £150k four years on). Of course, there may have been renovations at that point - the house has obviously had a new porch and windows at some point.
I can also check out graphs of the Land Registry's data in the area, so I can see that the number of sales per month in the area averages about 250 for the last few years, so I'd say that's a big enough sample size to be comfortable with.
As other replies have pointed out, using any online calculator can only give you an idea, and much depends on the market conditions at the time of any sale, but I designed the extension to let you do it quickly and easily, as an initial sanity check, and provide additional information and ways of looking at the data to give you insights and raise questions that otherwise would take much more time to get to.
It will also let you put the listing on "watch", where it will automatically notify you whenever the status or asking price changes which I find very useful.
It's free, and you're welcome to install and use it if you think it could be helpful
here.