There goes the neighbourhood. There was a time when north London's Bishops Avenue - or 'Billionaires Row' - was lined only by palaces, mansions and big houses. That time has gone. Now, flats are being built, and quite a few too - 53 at three developments. The latest launch was for developer Barratt's Allingham Court, where five of the 12 flats have been sold - three to British buyers, two to east Europeans. In a site surrounded by landscaped gardens the properties range in price from GBP3.9 million (HK$60.53 million) to GBP11 million and will be completed in June. They include 10 three-bedroom flats and two four-bed penthouses. Across the road is the Woods, where Willowacre Investments and Developments has built 14 stylish homes in three, four-storey blocks around communal gardens on a 0.4 hectare site previously owned by the British screen star, Gracie Fields. One flat has been sold to an Israeli buyer and two others are under offer. Prices range from #3.6 million to #8.5 million for the two, three and four-bedroom flats. Some have roof terraces. The prices for these apartments may sound steep, but are cheap compared with those paid for houses on Bishops Avenue, a 1.6km stretch which connects Hampstead with East Finchley. Next door to Allingham Court is Toprak Mansion which was sold for GBP50 million in January, making it the most expensive house on the road. At the less expensive East Finchley end of the avenue, Octagon Developments is building 27 flats at its Bishops Park estate. Prices of these homes start from GBP2.1 million. Historically, houses have often been knocked down to make way for new, flashier houses on Bishops Avenue. Now, developers are replacing some houses with blocks of flats to get returns that are perhaps double that of building a new house. They have found strong demand for these flats from second home buyers. 'We wanted to maximise the value of what we could build [at Allingham Court],' said Tim Foreman, a sales manager at Barratt West London. 'There is definitely increased demand from international buyers for this type of property, because they don't want the cost and complexities of running a big house.' Although smaller than neighbouring mansions, these homes were spacious Mr Foreman said. 'The apartments have house sizes,' he said. 'They range in size from 2,500 to 6,000 square feet.' Allingham Court's service charges are GBP6.40 per square foot, so the cost of maintaining a 6,000 sqft flat will be reassuringly expensive at GBP38,400 per year.