Looks like the first Elizabeth line train only gets into Reading at 7:40 which is boring as it means playing GWR's bike booking roulette...
Timetable is showing an Elizabeth Line 5.48 from Paddington getting to Reading at 6.40. That's the Saturday schedule valid until June. Whether it actually runs......
There's also a 6.18 ex-Paddington. Remember these are from Paddington Upstairs. If you arrive on the first ex-Abbey Wood train, there's ample time to surface from Paddington Downstairs [arr 06.05]
Alternatively, the start is only just over the bridge from Reading General so a 20 min late away day is no big deal if you take the direct train, arr 7.40. All FREE for FREEdom pass holders too! What's not to like?