No member of the British Royal Family is currently in the Line of Succession of any foreign Royal House.
Prince Philip and his descendants would have been in the Line of Succession to the former Greek throne, had Prince Philip not renounced all his styles, titles and rights to the Greek throne before his marriage to the Princess Elizabeth.
The only way a member of the British Royal Family could be included in the lines of succession of the current European Monarchies is if they actually marry into it. For example, if a theoretical daughter of the Duke and Duchess of Cambridge married Prince Christian of Denmark, their children would obviously be in the Line of Succession of both countries, unless otherwise stipulated by marriage treaties.
The Dutch Line of Succession is NOT limited to 11 people; rather, it is limited to those who are within three degrees of kinship from the current Monarch. If all those who enjoy such kinship were wiped out, the Parliament would either designate the closest relative by proximity of blood as the next Heir, or would just abolish the Monarchy altogether, depending on the circumstances.
The same would be true for other Monarchies, unless otherwise stipulated by laws of that country; for example, the Spanish Constitution clearly states that the line of succession is limited to the descendants of Juan Carlos I (though some interpretations allow the possibility that his siblings and their descendants, and even more remote relatives are included in the Line of Succession as well).
- Danish line of succession is limited to the descendants of the reigning Monarch.
- Belgian line of succession is limited to the descendants of the reigning Monarch.
- Dutch line of succession is limited to three degrees of kinship from the current Monarch.
- Norwegian line of succession is limited to the descendants of the reigning Monarch.
- Line of succession to the Liechtensteiner throne is limited to those individuals who comply with the rules of inheritance.
- Line of succession to the throne of Luxembourg is limited to the descendants of the late Grand Duchess Charlotte
- Line of succession to the Monegasque throne is limited to the descendants of Louis II (unless special stipulations are made).
- Swedish line of succession is limited to the descendants of the reigning Monarch (which means there are currently only three people in the line - Crown Princess Victoria, Prince Carl Philip and Princess Madeline).
- Spanish line of succession is limited to the descendants of Juan Carlos I (though some interpretations allow the possibility that his siblings and their descendants are included in the Line of Succession as well).
EDIT: My mistake, thank you for correcting!