How often do you check your tyre pressures?
+1
also get your car in for 4 wheel alignment - could be the front camber is out 
As far as i am aware u can't do 4 wheel alignment on a mk IV..only the front wheels can be adjusted
I would defo have the tracking checked ..
Yeah can indeed have 4 wheel alignment done but yes only the front wheels can be adjusted.
I said 4 wheel alignment as to me its different from tracking. Tracking only checks the wheels are pointing straight line. That's the way I've always understood it to be
When I had the 4 wheel alignment done they basically checked the whole lot, camber, toe and tracking.
As you have both said most will onyl be able to get the front wheel aligned with the tracking and as i found with my camber an toe beign way out = a sh!t feeling ride
the only solution was to get some rear adjustable tie arms which have sorted out my issues with the camber, at least now when i have it checked again if anyhtign has gone back out it can be sorted fairly easy