By Graeme Murray & Ed Chatterton A huge 25-bedroom country house that also served as a hotel has been sold, but for well under the price of an average semi-detached house when it went under the hammer. The Grade II-listed Otterburn Hall, in Northumberland, was built in 1870 and was formerly a luxury four-star hotel described as “one of the North East’s most opulent venues.” Set within a rural national park the 25,000fit sq pad has 16 acres of woodland, lawns, a fishing lake and a river. But its grand hall is now in desperate need of repair and its buyer will now have a major renovation job on …