I have knocking sound coming from the front wheel area. This increases with speed, as though something is catching on the wheel. Just had burst tyre replaced after small impact. Any ideas? Drives fine otherwise and only makes the noise when going straight.

 

Check the fixing clips on the plastic sumpguard panel or the wheel arch panels in front of the wheel.
Might be loose and flapping about with airflow movement under the car?

 

It's fairly common to break the sway bar linkage ball joint in an impact. The unconnected link may be rubbing against the wheel.