I don't use the motorway much but did a 350 mile round trip to visit my daughter in Surrey. It was all motorway and I kept the speed to 65 mph. I found it quite noisy, especially from the rear.
My previous cars were Audi A6 and SEAT Alhambra, both diesels, and they were significantly quieter.
Tyres will obviously have some effect on the road noise but by far the main reason is the lack of sound deadening/damping. The MK3 is already pretty good compared to previous generations but I guess to keep the cost and weight down Honda have had to skimp on the sound insulation.
In my previous car, the EP3 Type-R, it was the same. Once I put some sound deadening in, it made a much bigger difference than low noise tyres ever made.
I find with European cars, there is generally more sound insulation as well as thicker steel panels/doors etc which usually helps reduce noise.
I think if you want a refined Jazz, some insulation in the wheel arches, boot floor, doors and the firewall/bulkhead area will make a considerable difference. But having used the MK1 for over 10 years, the MK3 is already an improvement so we're not going to do any more.