You'll have to get lorries to speed up a bit. They are restricted, by speed limiters, to less than 60 already!
There is, in a sense, an offence of driving too slowly; it would fall under driving without due consideration for other road users. But drivers at 45 mph in the nearside lane have never bothered me. What does, is lorries overtaking one another in two lane motorways, such as on the M11, because they take an age to do it at 56 mph and I can't see why they bother, since the lorry they are overtaking is going at about 2 mph slower than they are. Meanwhile, they are holding up everyone else.