The midland mainline, coming to tsw on the 18th of april, has a lot of add-on potential, with a few highly suggested trains that could be added. Here is some of the stock which could be added. Class 170 (EMR/EMT) Operates similar services to the class 158 Class 156 (EMT/EMR) Operates peak services alongside the class 158 and 170 Class 222 (EMT/EMR) Operates express services alongside the HST Class 170 (XC) (Operates semi-fast services between derby and Nottingham) Class 220/221 (XC Operates express services between derby and Nottingham. Even just some of these could make the route feel more diverse and unique, with a current lack of british DMU stock in-game, this would be a great opportunity to add some of these.
For the freight train you might as well add the strongest British diesel locomotive class 60 to access the power station and Toton Marshalling Yard
The EMR 170 wouldn't be appropriate for the year the route is set in but the other units would be brilliant additions mate.
EMT never had 170s only EMR and as Matt said it would be the wrong Era but we could still get it with XC if the license is obtained