I have a cheapo bike ( worth maybe £70 used) its pretty scratched up with a ripped seat but still it's bright red so it still stands out and still looks decent when washed 
I don't really have a lock and I rarely leave it anywhere anyway,but I want to start commuting with it and it would suck if one day I come back and I don't have a way to get back home.
This is the lock I want to buy ( actually It's free because I have a credit on that site and I only want to get it because it costs me nothing and I need to spend the credit
)
https://www.ffx.co.uk/tools/product/Masterlock-Mlk8228E-3520190941930-1M-X-18Mm-Cable-Blue
I understand its not the cheapest poundshop lock, but still its a cable lock with just some added protection to the cable itself so probably not very good.
Is it worth to get it or am I wasting my time?

I don't really have a lock and I rarely leave it anywhere anyway,but I want to start commuting with it and it would suck if one day I come back and I don't have a way to get back home.
This is the lock I want to buy ( actually It's free because I have a credit on that site and I only want to get it because it costs me nothing and I need to spend the credit
)https://www.ffx.co.uk/tools/product/Masterlock-Mlk8228E-3520190941930-1M-X-18Mm-Cable-Blue
I understand its not the cheapest poundshop lock, but still its a cable lock with just some added protection to the cable itself so probably not very good.
Is it worth to get it or am I wasting my time?

) came out of it's skip pre-accessorized with a locked Squire D-lock attached around it's top and down tubes. Today I decided to remove it, so out came a pair of 30" bolt croppers. I was expecting to struggle, because the shackle diameter was right on the limit of the jaws, but I just did it in 4 or 5 bites, deepening the V in the shackle each time and pushing it deeper into the jaws. It took me no more than a minute and it didn't even make much noise. None of this standing on one handle and dancing about putting all your body weight on the other handle you see in security demo videos either. OK, I'm a good size and fairly strong, but it really wasn't a big deal, and I'd imagine a no-name Chinese cheapo D-lock would have probably been even easier and quicker to defeat. Don't assume that D-locks can't be cut just like chains or cables - they can!