Convinient to have a spanish will.
Convinient to have spanish residency for some tax benefits. Take into account that legally, all your patrimony ( even the UK assets) will accrue the Inheritance taxes here in Spain, but the substantive inheritance rules ( LAw) will always be the one of your nationality.
Art 6 of Inheritance Tax:
1.- TAx payers with residency in Spain will be obligued to pay the Inheritance tax in Spain, regardless where the assets or rights are.