Does the Wales service fill the gap?
Unless the ATW service is retimed. The departures would be as follows:
Birmingham to Shrewsbury
xx.00 - WMT - Sandwell & Dudley, Wolverhampton, Codsall, Shifnal, Telford Central, Wellington
xx.25 - ATW - Smethwick Galton Bridge, Wolverhampton, Telford Central, Wellington
xx.49 - WMT - Bescot?, Darlaston, Willenhall, Wolverhampton, Bilbrook, Codsall, Albrighton, Cosford, Shifnal, Telford Central, Oakengates, Wellington
Shrewsbury to Birmingham
xx.15 - WMT - Wellington, Telford Central, Shifnal, Codsall, Wolverhampton, Willenhall, Darlaston, Bescot?
xx.33 - ATW - Wellington, Telford Central, Wolverhampton, Smethwick Galton Bridge
xx.41 - WMT - Wellington, Oakengates , Telford Central, Shifnal, Cosford, Albrighton, Codsall, Bilbrook, Wolverhampton, Sandwell & Dudley
I think that the stops are right so that the services don't get stuck behind each other.