Nowhere near, though there are regional variations. The
latest available ORR statistics, for July to September 2022, indicate that only a few TOCs operated 95+% of pre-Covid train-km:
- Elizabeth line (obviously not comparable, due to the opening of the core section)
- EMR (again not comparable, due to the introduction of Connect services)
- Lumo (not comparable as didn't operate before Covid)
- London Overground
- Caledonian Sleeper
- Grand Central (they have since reduced their services slightly)
- Heathrow Express
The following TOCs operated 90-95% of pre-Covid train-km:
- Merseyrail
- GWR
- LNER
- Hull Trains (believe they are now back to a full pre-Covid service)
- TfW
There are many TOCs running a significantly reduced service compared to pre-Covid, including XC, Avanti, TPE, Chiltern, WMT, GTR, ScotRail and Southeastern. Most of those have now undertaken post-Covid timetable recasts which have baked in these reductions.
Greater Anglia, c2c and Northern have a moderately reduced service compared to pre-Covid.
Obviously you do also have to consider passenger-vehicle-km (see page 14 of the above-mentioned report), as some operators (notably XC) have lengthened services such that they are still running a similar number of coaches per hour, spread across fewer services. But maintaining a similar number of coaches per hour is no substitute for frequency; it is well-known that higher frequency tends to lead to higher demand.