Getting a little bit of mudguard rubbing on the Trek, so took a look under the brake bridge and it appeared there was about 3mm space between the bridge and the guard, but because of the mount I couldn't move the mudguard any higher. Ordered a replacement metal mount, and filed down about 3mm from the bracket (same mount I was using already, which was a replacement for the weak plastic mount that was causing a rattle). Used my lunch today to take the mudguard off, replace the bracket with the new modified one and refit.
The guard now sits a little higher on the tyre and there is a much smaller 1mm gap, so hopefully that will reduce the rub (only really happening when starting off from still when the load through the wheel is greater).