Having dealt at the nexus of citizenship and taxation matters with lawyers over the years and seen some blunders that arise from compartmentalized knowledge (even when including hand-offs between lawyers with different competencies) and some genius moves from those who don’t limit themselves in the hunt for information, I will say that there Is great use in using lawyers but also risk at times in relying upon just one lawyer (or even two or more lawyers) without also seeking out the knowledge and/or experience of multiple others ... lawyers and otherwise — when in the OP’s kind of situation.

Fortunately for the OP, there is a substantial enough community of Spanish Brits, and asking them — even online — can be enlightening;whether it’s about finding a lawyer already well-versed in Spanish and British citizenship and residency matters (including that related to taxes, estates/probate and/or family law matters) or to get a sense from others who have gone through the situation without using a lawyer and how that went.

This doesn’t mean to take everything or most everything said online in a travel forum,as gospel, but it also doesn’t mean that there is no useful citizenship information to be sourced on FT too. There is at times.