Had a bit of a bump a couple of weeks ago ,guy ran into the back of me damaged passenger side rear bumper and panels behind it,car goes in for repair on thursday, but ever since the accident seems to be a lot more road noise from the rear , could be just wind getting through where it should "nt i suppose but anyone have any other ideas.

Other than "make sure you tell the coachbuilder", no.

I had a simmilar problem when I was hit by a truck and needed rear offside panel replaced. The noise was from a poorly positioned rear windoe seal which is easy to do in an Octavia estate. Once new seal put in by coachbuilder, noise resolved

Depending upon the force of the bump, make sure you you get the rear wheel alignment checked.

There are a number of other threads relating to mis-alignment of the rear wheels causing noise and premature wear of the tyres.

I had a simmilar problem when I was hit by a truck and needed rear offside panel replaced. The noise was from a poorly positioned rear windoe seal which is easy to do in an Octavia estate. Once new seal put in by coachbuilder, noise resolved

I think most people would have "rear noise" if they were hit by a truck