It was roughly hourly to Crewe but only occasionally through to Birmingham, every 3 or 4 hours or so IIRC.
At its best under FNW, it was hourly Crewe-Holyhead, starting back at Birmingham in alternate hours.
But there were never enough working 3-car 175s for the intended service, and the service remained on slow LHCS times south of Crewe.
The through services stopped in 2002 when the WCRM project closed the fast lines between Crewe and Stafford for upgrade.
By the time that finished, Arriva were taking over from First and planning the diversion of Holyhead services via Shrewsbury which started in 2004.
At this point there were two ATW hourly shuttles Chester-Crewe, which were downgraded from 175/158 to 150/153.
Virgin had 3tpd HSTs London-Holyhead until 2003 when 5tpd Voyagers/57+390s started, increasing to 6tpd Voyagers today.
The hourly London-Chester Voyager started in 2008, replacing one of the ATW shuttles.