Fitzy - difficult to say without knowing more information - how long is the exposure how often, etc - all the factors that would be included in a good COSHH assessment. As for the MEL while the dust may disperse quit quickly I think there is a good chance that the air in around the operators head will become rapidly contaminated. Wood dust is not always easy to see but think about using a saw to cut stone - you can see the effect close to the cutting there very easily, and the HSE expect sensible suppression in those areas.

The requirement for LEV I would imagine would be SFARP - you can get mobile systems, even hand held tools have collecting bags attached to reduce the exposure risk, so your assessment needs to show you have considered all options and if you are relying on PPE alone why.

You should be looking for on tool extraction backed up by dust masks. Given the equipment out there and costs involved there is little excuse for not having it.