In reply to john arran:
For me, a NAS was the way to go for having all my movies, music, and photos in one place. I could then view, listen to or watch any movie from any device that could connect to router and NAS box.
However not all NAS boxes are made equal and as such, you do get what you pay for.
Some NAS boxes say that they are good media streamers in the marketing literature but in the real world struggle with more than one person in the house-hold trying to do stuff at the same time. You'd be hard pressed to buy a cheap NAS box that would allow two people to watch two different movies at the same time without buffering. And add a bit of music streaming into the mix and it could slow down completely.
Two of the reputable names for looking for good NAS boxes for the home are made by Synology and QNAP. There are others and some are cheaper but the saying is buy cheap, pay twice.
Another alternative, which can be cheaper or even completely free depending on what you have at home, is to use a spare computer as a Media Server. To begin with you could use your desktop computer with an extra hard drive shoved in it which is dedicated to storing media. Everything in the home then has access to this hard drive. Or, if you have a spare computer gathering dust in the house, then you could turn it into a dedicated media server for your music, movies, and photos.
These computers used as media servers act in the same way as a NAS box but have there differences. The first, is that they are considerably bigger in physical size than a NAS box and they would have to be kept constantly running to feed the media needs of the house. NAS boxes are small and use far less energy. The benefits of a spare or dedicated computer taking the role of a media server is that they can have shed loads of RAM and processors that domestic NAS boxes can only dream of. This extra RAM and processing power is excellent for streaming a couple of movies around the home and playing music at the same time, provided your home router is up to the task of sharing all this media goodness out to everybody.
I started my media server path by starting off by using my desktop computer and from there moved onto a cheap NAS box bought from PC World. The cheap NAS box worked well however I soon realised its limitations in speed and multi-tasking. The hard drives eventually died and at that point I invested in a fairly decent NAS box from Synology. These boxes can easily cost the same price as a good quality desktop computer but you have to remember that they are small to be energy efficient especially as they will be switched on 24/7 365 days a year. Many NAS boxes are near silent. A home computer is nowhere near as quiet so you may want to stick it somewhere out of the way if you don't like the sound of fans whirring around.
https://www.qnap.com/en/
https://www.synology.com/en-uk