stu, it's never easy but you did the right thing. Far better to dispatch humanely.
It is a real struggle to rehome cockerels and the down side to breeding and keeping chickens or buying in eggs or chicks.
If you do rear youngsters I feel its better to cull them earlier rather than later. Once you are more used to keeping them, identifying young birds and then dispatching them. Often easier when smaller as you can handle them better. Plus the cold hard fact is that most people don't want or need cock birds and unless suitable for breeding and so many are superfluous.
The other alternative if you have room and funds is to bring on young birds and rear the males with the intent to eat. You can rear them for 3-6 months and then finish and freeze (or if only one at a time, then eat fresh). I find it worked well for us when we bred birds as it at least meant the birds had some purpose and it wasn't just a wasted life.