Thanks for replies.
Off-Peak Day Return tickets are not valid on the 08.57 from Worcester to Ashchurch (next station). Difference in price between Off-Peak & Anytime Return is just 5p (^4.70 and ^4.75)
So the only option from where I live is Cradley Heath to Ashchurch anytime return at ^9.05 instead of ^5.55 Cradley Heath to Worcester return. Extra cost is ^3.50, so save money by cutting back on cups of tea during the day! Surprising how expensive just a few minutes can be!
Looks like it is still a practical proposition for a couple of good days out during the 7 day period.
Another option, allowing a later start, but still getting you to Taunton at the same time if you went via Worcester would be to go via Birmingham. You can do this with a Cradley Heath to Ashchurch Anytime Day Return (route - any permitted) for the railcard price of ^12. Okay it means even fewer cups of tea, but you could always take a Thermos^!!
You could take the 0824 from Cradley Heath to Birmingham Moor Street arriving 0849, do the short walk to New Street and catch the 0912 CrossCountry service direct to Taunton. Even though this train doesn't call at Ashchurch you would be permitted to combine the Cradley Heath to Ashchurch Anytime Day Return with your Severn & Solent Rover. This is allowed under the National Rail Conditions of Carriage:
19. Using a combination of tickets:
You may use two or more tickets for one journey as long as together they cover the entire
journey and one of the following applies:
(a) they are both Zonal Tickets (unless special conditions prohibit their use);
(b) the train you are in calls at a station where you change from one
ticket to another; or
(c) one of the tickets is a Season Ticket (which for this purpose does not include
Season Tickets or travel passes issued on behalf of a passenger transport
executive or local authority) or a leisure travel pass, and the other ticket(s) is/are not.
You must comply with any restriction shown on the tickets relating to travel in the trains of
a particular Train Company or Train Companies (see Condition 10).
If you do not comply with this Condition, you will be treated as having joined the train
without a ticket and the relevant parts of Condition 2 or 4 will apply, either to the entire
journey, or from the last station where the train stopped at which at least one of the
tickets was valid.
For the purposes of this Condition, a ^leisure travel pass^ means any multi-journey ticket
(excluding Season Tickets) valid for:
(i) at least 7 consecutive days; or
(ii) at least 3 days in a period of at least 7 consecutive days
and includes rover tickets, travel passes, flexipass tickets and Britrail passes.
I've highlighted the relevent parts of the condition. This is a useful rule for anyone combining tickets for travel into an area for which they have a rover ticket. There is no need to use a train that calls at a boundary point, it merely has to pass through.
Hope I haven't overloaded you with this alternate option. You may desperately want to trundle from Worcester to Cheltenham in a (likely) draughty Class 150, but I'd prefer the slightly more expensive, but quicker option of going via Brum - even if it does mean travelling more miles with CrossCountry!