I have one of these
netgear
Very relaible, I havent rebooted it in over 2 years. Other brands are available such as qnap, iomega etc etc. Ebuyer sometimes have good deals.
You can buy one pre-populated with drives, or unpopulated which may save you a few pounds but if you ain’t too hot with the computaz probably easier to buy with the drives already in.
One feature to look for is mirroring or RAID1 (the same thing) which means one drive is a copy of another so if one fails it keeps on trucking with no data-loss, although you do then only have half the capacity (e.g. you buy one with 2x1TB drives you only get 1TB for your files as the other drive is a copy, rather than 2TB space). But i’d say it was worth it.
Also depending on how much data you have how many drives (bays) it can take can be a factor, but generally for home use one that takes 2 drives should be ok….
Dave