Sorry - just following the guidance from a well known tax adviser:
UK Residence Rules - A Real Cause for Concern
The rules which govern UK residence were well understood by British expatriates. At their core the current guidelines state that expatriates keeping their visits to the UK at less than 91 days per year are viewed by HM Revenue and Customs (HMRC) as non-resident.
Other conditions to the guidelines of course apply, but the heart of this rule has provided expatriates with a clear view of what was needed to maintain non-resident status. The guidelines have also provided a framework to those who work or have retired overseas – even if a property has been retained in the UK.
When a review of the Residence and Domicile rules was announced by the UK government in 2002, many were concerned that serious changes would follow. In 2007, the Govenrment finally announced that the review was complete and that, from April 2008, it will ‘introduce changes to the residence rules so that days of arrival in and departure from the UK will count toward establishing residence’. This is a blow for expatriates who will need to ensure they carefully plan any visits back to the UK.