Thomson 28WT25U S picture problems

I hope you can help me with a picture problem.

I have a Thomson Model 28WT25U S which has developed some vertical “Bands” on the left hand side of the screen. – Please see attached picture.

These bands have developed over recent months and are worse with lighter backgrounds – They tend to distort the picture.

The Bands on the very left hand side of the screen are from top to bottom. The bands get shorter the nearer they are to the centre of the screen. (The bands encroach about 3 to 4 inches “in” from the left hand side).

Can anyone explain what these might be ? – Note, I do not have any magnetic interference anywhere near the T.V. also the set is about 4 years old.

I know how to access the service menu if anyone can suggest a cure.

Many Thanks

Paul.