We are looking for an active not too strenuous bike tour . Has anyone done a bike tour in the New forest park ?
As b.Paul 1 could have more helpfully written it is the New Forest National Park.
I'm sorry I don't have any answer to your actual question for you.
There are multiple bike routes within the national park. By "Tour" do you mean organised or guided? Over what sort of distance? The forest is mostly flat - in that there aren't many long or steep climbs - but it's certainly not the Netherlands.
I suppose the important questions would be "Where are you going to be based" and "do you need to hire bicycles?"