The original track access application did show the additional Exeter extra as 159 operated:
http://www.networkrail.co.uk/browse%20documents/track%20access/2%20completed%20consultations/2015/2015.02.23%20sswt%2058th%20sa%20-%20section%2022%20-%20closes%2023%20march%202015/58th%20sa%20form%20p.pdfThe very last couple of pages lists the intended stock for each service.
This extra down from Yeovil:
SX 14:50 Yeovil Pen Mill to Exeter St Davids 1x159
then these two:
SX 16:36 Exeter SD to Honiton 1x159
SX 17:07 Honiton to Exeter St Davids 1x159
I assume the '2 tph between 1600 and 1800' includes the existing off pattern extra service to Axminster?
Edit, yes, the full
SWT▸ news item makes this clear, if you follow the asterisks to the 'notes for Editors', I've edited it to join the info up:
Two trains per hour from Exeter to Honiton between 16:00 and 18:00** / **currently only 2 train per hour 17:00-18:00
and
Half-hourly train services from London to Tisbury, Gillingham, Templecombe, Sherborne and Yeovil Junction between 15:20 and 19:20* / *today it is half hourly 16:20-18:20
The whole news release is here:
http://www.southwesttrains.co.uk/NewWestofEngland.aspxPaul