UK succession is strikingly different from civil-law Europe, and the EU framework does not bridge to it. This focuses on England and Wales.
The EU rules do not apply
The UK is not bound by the EU Succession Regulation. English conflict-of-laws rules apply instead — broadly, the law of the place where land is situated for immovables, and the law of the deceased’s domicile for movables.
Testamentary freedom
England and Wales has testamentary freedom — there is no forced heirship, so in principle you can leave your estate as you wish. (Scotland is different: children and a spouse have legal rights / legitim over part of the moveable estate.)
The 1975 Act safety valve
That freedom is tempered by the Inheritance (Provision for Family and Dependants) Act 1975, which lets a spouse, children and certain dependants apply for reasonable financial provision if the will (or intestacy) leaves them out.
Probate and tax
The estate is administered through a grant of probate (or letters of administration), and Inheritance Tax (IHT) turns on domicile and the location of assets.
For foreign families
Because the EU rules do not connect to the UK, a continental will may not work as expected. A verified UK colleague (solicitor) can confirm the applicable law and run probate.
Domicile and tax rules change — confirm with admitted UK counsel.