Switched on my TV today and i have sound but no picture. There is just a line on the screen going from top to bottom. Have a feeling its the tube thats screwed. Any ideas guys?

Sounds like a faulty frame ic, if tapping the side of the set restores the picture then possibly a dry joint.

Is this a major problem cost wise to get fixed?

If the line is vertical is a line stage problem, if the line is horizontal then it is a frame stage problem. Cost, difficult to estimate ask a local TV repair shop.