Towcar advice Bailey Olympus

westiek

We currently have a Suzuki Grand Vitari, which although has plenty of kerbweight capacity for the van has absolutely no 'oomph' what so ever!! I am aware the max speed when towing is 60mph but on our first foray onto a motorway we struggled to get above.
45mph!! I fear the 2litre engine is just too small. Any recommendations  of what we should look at getting? not a range rover / land rover please due to mpg. Thanks