I've had a few over the years so I'll briefly explain.
There are multiple, some better than others, which it's why it's important to sign up monthly, and always take advantage of the 24 hour trial, even if it's a few quid.
Sometimes they go down for a few hours to a day, and it always seems to be on a match day in my experience, however 95% of the time it's great. The stream quality will largely depend on your quality of internet, and something people often overlook is the modem you have. If you've got one older than 3 years, it's time to go out and spend £100 on a new one, it will improve your internet connect and speed to no end, honestly.
IPTV's are targeted often by hackers and groups who try to shut down the service or hold it ransom, sometimes they're successful and one day it goes down and never comes back.
All in all, I've been using IPTV's for about 8 years, in that time I've had very little downtime except for twice the service was hacked and shut down. If you keep a monthly subscription you only ever pay £10 a month so if it does get shutdown you lose maximum a tenner, so the risk vs reward is minimal IMO.
Take to Reddit for advice on the best one's currently, check the list and try the top 5 on 24 hour trials, see which one works best for you.