Just to report a couple of probably unrelated issues encountered at the same time.
Firstly, my game is in 1848, I have the LBSCR Jenny Lind and LWNR Crewe Type locomotives available, with top speeds respectively 95km/h and 90km/h. However, the only track available is "Wrought Iron Track" 60km/h, which doesn't seem quite right.
Secondly, I have Jenny Linds pulling rakes of 10 100km/h LWNR coaches, which should obtain a Max Speed of 70km/h according to the Depot dialogue. However, the train refuses to accelerate past 50km/h. Occurs to me that possibly the 60 km/h track is in fact coded at 50km/h?