As someone who used to live in Armitage and occasionally used the Trent Valley service from Lichfield in the 1980s and 1990s, the original local service was for many years a Rugby or Nuneaton to Stafford EMU, running at odd times on a roughly two to three hour cycle, serving Nuneaton, Atherstone, Polesworth, Tamworth, Lichfield TV, Rugeley and Stafford, timed to make connections into Inter Cities at each end. Normally it was a Class 304, fun for the guard as Atherstone, Polesworth and Rugeley were all unstaffed and the 304s were non-corridor. In addition, Lichfield got two Inter Cities in the morning to London, one about 06.30 and another an hour or so later, and two back in the evening, one about 6 and another about 7pm. Lichfield TV of course had short platforms then so most of the train was off the platform. These trains were quite well used when I caught them in the 1990s. In about 1993-4 Inter City started stopping the first Glasgow daytime departure out of Euston at Lichfield, which gave Lichfield a morning northbound service even though it was virtually semi-fast to Glasgow. I did it once on a Railrover just for the novelty of going direct from little Lichfield to Glasgow. Tamworth always had a slightly better inter City service than Lichfield, probably a throwback to when the electrification scheme was introduced and places like Burton on Trent were intended to be more quickly served by connections at Tamworth than going up to Derby. However, if I recall correctly the service frequency varied throughout the day.
In the 1980s the electric all shacks was replaced with a DMU which turned off at Nuneaton to go to Coventry. I briefly worked in Atherstone in the late 1980s and we were warned not to bring our cars into town on Atherstone Ball Game day as they might get damaged by the ensuing riot, so the early TV local DMU from Lichfield to Atherstone was very useful on those days, I do recall a very pleasant trundle down the WCML on a Class 108 one Shrove Tuesday.
The basic pattern remained the same on privatisation apart from the short lived North West Trains Manchester Airport to Euston service, which used the ex Stansted Class 322s, stopping at Tamworth. Again, I did sample the service once just to try it out, driving down to Tamworth to pick it up.
The current level of service along the Trent Valley is probably the best it has ever had in terms of frequency and usefulness to local communities along the line.
By the way, there was a Stansted to Liverpool via Birmingham and Stafford service for a while in Central days, it was simply the Stansted to Birmingham set working forward on a Birmingham to Liverpool diagram which occasionally saw DMU operation. Again I once caught it from Stafford to Birmingham so I know it ran at least once!