Within the UK, the individual has freedom to decide how to distribute their estate on death (assuming they make a Will). That is not the case in many other countries and certainly not in France or Spain. This is an important area on which to seek advice before a purchase is made, otherwise property may not pass on in the desired way.
For example in France it is the location of the property, not the residence of the owner, which determines how the property passes. French inheritance law divides the property in a strict order as follows:
The position of the spouse is clearly not advantageous, although it is possible to improve that by making an election for the French universal matrimonial regime to apply or to ensure that a French Will is made. This is a very important area on which local legal advice should always be taken.
Spanish inheritance law is more generous to the spouse. It requires 2/3rds of the estate to go to the closest heirs and the remaining 1/3rd can be distributed freely. From the 2/3rds, 1/3rd must be for the spouse for life. It is important to take local professional advice and to ensure you have a Spanish Will.