Suzuki Club UK

I'm in the UK and my car is an automatic. It creeps when I'm in reverse/drive and I'm not braking.

Today when I went to reverse out of my driveway, it didn't creep backwards when in reverse. Instead, it just rolled.

I tried a few times, putting on the handbrake and putting it into park, leaving it for a few seconds, then trying again. Each time it would just roll forwards with no creeping.

When I was about to hit the wall I pushed the accelerator but I think I was too late, the car didn't respond and I scraped my bumper on the wall.

I got out, rang my brother and had him walk me through it all and it worked once I tried it again. The car crept backwards as it has every other time I've reversed out of the drive since getting it.

I guess my frustration is that I really don't understand what went wrong and how I messed up. Is there something I could've done to prevent the car from creeping and instead cause it to roll forwards?

I was 100% in reverse, handbrake off and brake released.

The answer to your question

Is there something I could've done to prevent the car from creeping and instead cause it to roll forwards?

is yes, put your brake on. Is your driveway on a slant by any chance? I don't get what your problem is really.

As Tim posted - is your driveway on a slope ?
Does your car have a rev counter ?
An automatic will only 'creep' if the engine idling revs are high enough,especially if on a slope.

It sounds a bit like a problem I had with an automatic Shogun, an electronic intermittent gremlin. A faulty sensor would ask for more juice without warning and if in drive, it would drive. It did this unexpectedly in town one day nearly running me into the back of the car in front. It went back to the main dealer and £400+ pounds later they solved the problem.
The fact your accelerator did not respond when you needed it? I would have a diagnostic done.