I've lived through changing the clocks in the UK for years but I still have to stop and think about it every time it happens. For my own sanity, I'm writing down a definitive guide to this slightly bizarre custom.
The basics
Spring forward, fall back.
The clocks go forward an hour in the spring and go back an hour in the autumn. Specifically, this happens on the last Sunday in March and the last Sunday in October.
The change happens at 1am in the spring and 2am in the autumn (obviously). This means in the spring you lose an hour of sleep but in the autumn you gain an hour.
Between the spring and autumn change the UK is ahead by an hour on British Summer Time (BST). The rest of the time it's on Greenwich Mean Time (GMT).
(thanks GOV.UK)
Consequences
When the clocks go forward, the sun will come up an hour later and go down an hour later. When the clocks go back, the sun will come up an hour earlier and go down an hour earlier.
If you forget to change your clocks, in the spring you'll be an hour late for everything. In the autumn you'll be an hour early.
Dealing with the change if you have children
If you have children 5 years or under in a regular sleeping pattern, things are a little bit backwards.
Let's assume for the sake of simplicity that your children always wake up at 7am - they might have one of those light up clocks that tells them when it's time to get up.
Spring (forward)
In the spring, when the clocks go forward, they'll wake up at their 7am, which has now become the world's 8am, so you can pretend they've slept in for an hour even though they'll have slept for the same length of time.
If you get them up at the new 7am they'll have slept for an hour less (like you) which may or may not be good. One benefit of this is that they might be more tired by the end of the day, and sleep in a little on Monday. But this is only a possibility.
Autumn (back)
In the autumn, when the clocks go back, they'll wake up at their 7am, which has now become the world's 6am. That seems like they'll have got up an hour earlier, but you'll both still have had the same amount of sleep (unless you went to bed an hour late thinking you'd gain an hour).
If you want to try keeping some normalcy you could put them to bed an hour later. But kids are unpredictable, so anything could happen.
Caveat
I think this is all correct. But I've just lost an hour of sleep, so what do I know.