It depends on the size and type of extension. Small porches or flat roof extensions are very reasonably priced. More substantial two storey extensions can be expensive. In general, the price is roughly proportional to the amount of space you add to your home.
Ellesmere
Ellesmere is a market town near Oswestry in north Shropshire, England, significant for its proximity to a number of popular Meres. The town is located alongside Ellesmere (aka 'the Mere'), among the biggest all-natural meres in England outside the Lake District and among 9 antarctic meres in the area. ('antarctic' suggests that the clinical depression inhabited by the mere was the location of a block of ice that persisted at the end of the last Glacial epoch). These meres are different from those in the Lake District because they do not have a flow of water right into them to keep the degree. A synthetic island in the Mere was created in 1812 from dirt dug out throughout the production of the gardens at Ellesmere House. This was later called Moscow Island, as Napoleon was compelled to pull back from Moscow that year. The Mere has a visitors' centre as well as is preferred with birdwatchers, many of whom check out to see grey herons nesting. There are eight various other meres nearby: Blakemere, Colemere, Crosemere, Kettlemere, Newtonmere, Whitemere, Sweatmere and also Hanmer Mere. The civil church which constitutes the town is Ellesmere Urban; the bordering parish, covering a large rural area, is Ellesmere Rural.