u/Chrismurphy01

I'm travelling to London from Dublin for the day. Arriving at Gatwick Airport, travelling down to Winchester, then flying home from Luton Airport, all in the same day. I've mapped out the journey, and it looks like I'll be using the Southern, South Western Railway and Thameslink services.

Is there any sort of Day Pass/Cheaper option I can avail of to use on all of these, or do I just purchase tickets for them separately with a journey planner?

Also, would it be advisable to book these tickets in advance or can I just pay when I get to London?

Appreciate the help.