Your suggestions

Trains is a good one to start with, PT-wise.

Get Emotional Winter from Anathema.

(These are good starting points, not necessarily the best songs)
 
Porcupine Tree:
Trains
Last Chance to Evacuate Planet Earth Before It is Recycled
Blackest Eyes
Lightbulb Sun
Piano Lessons
Pure Narcotic
Basically anything off In Absentia...
I only have these 3 PT albums :(

Anathema:
Angelica
Regret
Fragile Dreams
Lost Control
Deep
Parisienne Moonlight
One Last Goodbye
Barriers

UGH, sorry for suggesting too many songs.
 
Anathema: get the last three albums, then work your way through the remainder of the catalogue.

Porcupine Tree: get the last three albums, then work your way through the remainder of the catalogue.

Both bands should only be listened to in album form and are not served well by random downloading...