The 2018 service pattern has been announced with some peak variants so the Bedford to Littlehampton service 'route only runs Bedford to Three Bridges and Littlehampton to West Hampstead in AM peak.
http://thameslinkprogramme.co.uk/sites/all/files/article-pdf/Thameslink Core tph update_May14_v7.pdf
Services are all 2tph
Peak
1. Bedford to Brighton
2. Bedford to Three Bridges
3. Bedford to East Grinstead
4. Bedford to Littlehampton~
5. Luton/St Albans to Sevenoaks*
6. Luton/St Albans to Maidstone East*
7. Luton/St Albans to Sutton via Mitcham*
8. Luton/St Albans to Sutton via Wimbledon*
9. Peterborough to Horsham
10. Cambridge to Brighton
11. Cambridge to Tattenham Corner
12. Welwyn Garden City to Caterham^
* Wimbledon Loop services start Luton and terminate at St Albans in AM peak and reverse in in evening peak. Sevenoaks/Maidstone East services do the opposite.
~ Only runs in peak flow between Littlehampton and Three Bridges and West Hampstead and Bedford
^ Only runs in peak flow between Welwyn Garden City and Finsbury Park
Off peak
1. Bedford to Brighton
2. Bedford to Gatwick Airport
3. Doesnt run
4. Doesnt run
5. Kentish Town to Sevenoaks
6. Doesnt run
7. St Albans to Sutton via Mitcham
8. St Albans to Sutton via Wimbledon
9. Peterborough to Horsham
10. Cambridge to Brighton
11. Cambridge to Tattenham Corner
12. Doesnt run