Heater (94' TDi)

Just got back after a good 60 mile drive in the freezing Somerset Countryside. That heater never seemed to get any warmer than a luke warm! Is this a feature or is there a mod to get it to be more efficient (ie warmer!)

Check the basics, is the engine getting warm enough? If it is check if the heater control valve is opening all the way, is the heater matrix blocked or does the matrix need bleeding. Having said that i had a classic range rover which had a terrible heater which i never managed to get working well. Bought a big coat!