They did extend a number of Manchester to Bristol services to Exeter, though. It means that the spread of express trains from Bristol towards Exeter in the middle of the day is now far more even, if rather odd at times:They don't have the stock for what they are operating now, let alone adding to it.
1045 Plymouth
1115 Paignton
1145 Plymouth
1245 Plymouth
1310 Exeter St Davids
1345 Plymouth
1445 Plymouth
1509 Exeter St Davids
1545 Plymouth
1609 Exeter St Davids
1645 Penzance
1711 Paignton
1745 Penzance
1811 Exeter St Davids
1845 Penzance
1947 Plymouth
There's a slightly odd gap just after 1900. Of course, it doesn't actually need to be an XC train that fills it - there are stopping services at 1855 and 1914 but they do not get you to Exeter significantly before the 1947.