>>> can this person get out of paying me my owed money?
Legally, 'No'. Practically (possibly), 'Yes'.
If someone owes you money and won't pay up, all you can do (that doesn't involve employing a couple of big guys with baseball bats) is to take the matter to court. As that involves paying a fee to start the process rolling, it can be be somewhat impractical where the amount owed is relatively small. So, in practice, it's far easier for someone to get away with not paying £70 than it is to not pay £700 or £7000.
However the threat of court action can often be enough to jolt people into action. So hinting that you're prepared to go to court to get your money (even if you're not) might be worth a try.