I don't beat myself up. I had 3 offers. 2 for 18k and one for 17k for the government. The fact I had 3 offers but nothing before that for 6 months was probably an artifact of getting better at interviewing. The job I eventually got I was accused of being "too polished".
The highest starting salary I applied for was 25k, and the highest I heard anyone get was 40k, but working on a trading desk for 12 hours a day.
I graduated in 2014 and also started on £18k, as a junior C++ programmer :P Don't beat yourself up on it.