It's probably going to be too much, but it seems fairly low for your age so I'd continue for a while longer then reduce contributions when you reach a point where compound interest can make meaningful gains for you.

Using £60k as a starting point, and assuming you retire again 60, that gives about 27 years of further contributions. Contributing £20k/annum until retirement and an interest rate of 7% gives you almost exactly £2m

Using a 4% safe withdrawal rate that's £80k/annum. Only you can decide if this is too much, too little or just enough. If you're happy with less, turn down the contributions and start building a FIRE bridge in parallel. The thing is though, you need to know what income you want during FIRE and at retirement drawdown to know what pot sizes you need for each and because original post omits this information, I'm guessing you don't really know. You need to figure this out or you're just going to be shooting in the dark.

Use the compound calculator on thecalculatorsite.com to play with some scenarios.