It is an f4.5-5.6 - which is very slow. "Slow" meaning that it does not let in a great deal of light, hence results in slow
shutter speeds. Not necessarily slow in autofocus, as some people assume - but slow in shutter speed.
A "fast" lens, on the other hand, is one in the f1.2-2.8 range. These are usually big, heavy and expensive. But that's what is needed if you want fast shutter speeds in anything less than excellent light conditions. And since you're in the UK, you'll know that excellent light conditions aren't exactly the norm here
If you want to take action photos, you need a fast shutter speed. Without it, you'll have blurry photos whatever camera you're using. The better the light, the faster your shutter speed will be. Considering that great light in the UK isn't that common, you should probably consider a faster lens to take those sorts of photos. They're not all incredibly expensive.
In the meantime though, you would improve the photos by increasing the ISO as far as it takes to keep your shutter speed up over 1/500 sec (I'd suggest closer to 1/1000). That may often mean ISO800 and above. It will increase the noise, but at least the photos shouldn't be blurred.