Just in case it isn't clear, the human-readable time restrictions on the linked BR Fares page are identical to those on the linked NRE page; the BR Fares ones are simply formatted differently in an attempt to be easier on the eye to read.BRFares shows the restriction code to be 5X
www.nationalrail.co.uk/5X has the time restrictions. The only ones that appear relevant to this flow are the ones concerning Paddington and Reading