Whether or not you are a fan of the Royal Family a lot of the security costs will be in place because of other important members of RF : ie the Queen & Prince Philip plus the aunts and uncles and cousins of the bride. As Eugenie is a princess by birth her parents probably see this as natural for her to have the same kind of wedding as some of her cousins, and probably some of the smaller ones will be in the bridal procession too.
ITV are covering this as BBC apparently declined after weighing up the costs involved against probable viewing figures.
Princess Ann,s children were not in fact entitled to a title in their own right. As she married a commoner (Mark Philips) who was offered a title by the Queen which he declined, this meant his own children could not be titled. Children whose father's are princes are automatically titled, whereas in the case of a princesses' it depends on who they marry.
As for them living together for so long, well so did William and also Harry and Zara, this is what many couples do these days, and it's their choice just like many people do. I think once they all want to start a family it would be unacceptable by the RF to remain unmarried.
Just like any other bride I hope Eugenie and her husband to be have a lovely day, royal or not.