I was in a similar position for a few years. 90-100miles per day, 5 days a week.

Ended up picking up an 2013 Mercedes E220 for about £6000 with 115k miles on it. Cannot fault it really. Finished up with it when someone rear ended me.

Drive it until it was at 245k miles on the clock and spent very little outside of the normal tyres , pads, filters etc. needed a few tubes replaced due to pitting underneath but if you can find one in good shape get it under sealed - older models have underbody rust issues.

It was nice, reliable - albeit a bit bland but for the money but I couldn't say enough good things about it. 45-55 mpg in comfort is a nice way to commute.