From the FGW website :

17:40 Guildford to Reading due 18:19
This train will be started from Ash. It will additionally call at: Ash. This is due to congestion caused by earlier delays.

Customers travelling from Guildford to Ash are advised to travel on the 1746 service.

19:16 Gatwick Airport to Reading due 20:37
This train will be revised. It will additionally call at: Betchworth, Dorking West, Gomshall, Chilworth, Shalford, Ash, Farnborough North, Sandhurst and Crowthorne.

18:43 Redhill to Reading due 20:20
This train has been cancelled. This is due to a member of train crew being unavailable due to sickness.

17:04 Reading to Redhill due 18:31
This train will be cancelled. This is due to a member of train crew being unavailable due to sickness.

Customers travelling from Reading to Redhill are advised to travel on the 1734 service.

17:26 Gatwick Airport to Reading due 18:52
This train will be terminated at Redhill. It will no longer call at: Reigate, Dorking Deepdene, Dorking West, Guildford, Ash, North Camp, Blackwater, Wokingham and Reading. This is due to a member of train crew being unavailable due to sickness.

Passengers travelling from Redhill to Reading are advised to travel on the 1743 service.