For an unknown reason the tuning of the TV stopped working. 

At the beginning the tuning went off slightly and corrected itself, than the issue got worse and worse, you had reception, than you did not.

Now its so bad that when you run an auto or manual tuning no TV stations are recognized.

I have a VCR attached which I tuned at the same time about 7 months ago and the reception of the programs is still OK - so all I can do is flip channels through on the VCR instead of using the TV.

Would appreciate any ideas you may have.

I suspect........... a tuner failure!!!  Frustrating nonetheless but you did not specify whether it was an internal analogue or digital tuner.  If it is the former, you don't have a digital tuner and your set is no longer under warranty, personally I would not bite the bullet, just invest in an external Set-Top Box with Digital Freeview and perhaps a hard disc to record upon.  You'll have to do this anyway in the medium term if you have only an analogue tuner source so I would like to think of it as now really a problem, just bringing costs forward!  (You have to adopt strange approaches sometimes to justify further expenses!)

Then again if it is an internal digital tuner and your set is no longer warranty I would do exactly the same on a costs basis.