Hi there, i'm new here, i just found this forum. 
I own a super-off-peak return (in 1 month) from Exeter St David to Heathrow Rail, outward with 01:07-04:03 GWR to reading, 04:35-05:13 from reading to Hayes & Harlington, and 05:23-05:39 Elizabeth line to Heathrow T2&3, in 07-APR-25 (Monday). I bought it from Trainline and it shown me this route. (I have a seat reservation certification for the first portion)
I am struggling with whether it is legal to the transferring train departs Reading after 04:29, as well as the Elizabeth Line that follows.
I also can't find some relative information on national-rail-restrictions.
Thank you very much for your response!

I own a super-off-peak return (in 1 month) from Exeter St David to Heathrow Rail, outward with 01:07-04:03 GWR to reading, 04:35-05:13 from reading to Hayes & Harlington, and 05:23-05:39 Elizabeth line to Heathrow T2&3, in 07-APR-25 (Monday). I bought it from Trainline and it shown me this route. (I have a seat reservation certification for the first portion)
I am struggling with whether it is legal to the transferring train departs Reading after 04:29, as well as the Elizabeth Line that follows.
I also can't find some relative information on national-rail-restrictions.
Thank you very much for your response!