Never too late. If you have it you have it, being a spotter etc is certainly not a prerequisite. ATC can be a long hard road, and for all I love my job I don't know for sure if I would be pleased if my son followed suit. I suspect in 30-50 years max there won't be a job to aspire to. However, right now, if u can get an opening it's a pretty good job.
If you decide it is definitely what you want to do then go for it go via NATS, Serco , or whatever route opens up through your applications and investigations. Nothing ventured nothing gained.
For what it's worth, my career came about through speculative application, tip offs from friends of friends, and being in the right place at the right time.
Best of luck