The UK tax year that started on 6th April introduced a new Residential Nil Rate Band for inheritance tax. Changes to the domicile regime were also meant to come into effect then, but these have now been put on hold until after the June General Election.
Liability to UK inheritance tax is based on domicile, not residence. If you are a UK domicile, or are deemed domiciled under HM Revenue & Customs rules, your worldwide estate above £325,000 is liable to tax at 40%. Assets in the UK are liable regardless of domicile.