If he's in Rec probably take forever. If you think he has natural ability you need to be proactive and ask about a 'trial' with the head coach to get into squad. They can assess natural flexibility and natural strength, also ability to take instruction. Squad gymnasts are generally really mature for their age. Unless he's the male equivelent of Simone Biles, he could sit in Rec for years.
My daughter was doing 12 hours a week by the age of 6 on a squad (started after a trial at age 5 doing 8 hrs a week) which progressed to 20 hrs a week by age 8. 20 hrs a week cost us £90 a month. The rec kids fund the elite squads basically. That's why you're paying £60.
If you want him to be 'good', get him off rec would be my advice. If you're doing any kind of 'badges', they're not interested. Squad kids do Grades.
Having said all of that, I wouldn't recommend gymastics to anyone. It's destroyed my daughter and I'm still dealing with the fallout 2 years later. If you've ever watched Dance Moms, it's like that but 100 times worse in terms of how they talk to your kid and how they view them. Nothing is ever perfect enough. Coaches have their favourites, another coaches kid will simply jump through squads without having any skills and get way more attention than anyone else, your kid will be fatshamed from the age of 6 and told they're not behaving like an athlete, judges at competitions will deliberately mark you down to make a point, head coaches will threaten you with rec if you even raise a simple issue..I could go on and on. Read the Whyte Report - worst bit, it didn't even surprise me in the slighest, my daughter has been through worse and I didn't report it as it was 'normal'
My daughter was decent. She was doing a round off flic and back tuck at 6 and an upstart at 6 too, giants by 7.
She plays netball now, fabulous sport. Gymastics needs a serious overall.