Nothing more you can do but to replace the screen. Average price for us to replace a 15 screen is £110-£130 plus carriage.
My screen has lines running down it
More often than not, this will result in a new screen (see prices above) however it could just be the Screen (LCD) cable and would need to be checked out by an engineer. If just the cable, you are looking at £60-£80 plus carriage.
My screen has gone blank/dark but there is power to the laptop
In order of failures, you will require a replacement FL Inverter, LCD cable or repair to the lid micro switch. Rough prices are £60-£80 plus carriage.
The colour has faded on my screen and or charachers have gone funny
Typically, the video card or LCD cable is faulty and needs replacing - this is an especailly known fault where NVIDIA is the manufacturer of the video card. On many laptops, the video card is built in to the system (mother) board and would need replacing and that is when is can become expensive or as we would term, BER (beyond economical repair).
There is a large vertical bar or half the screen is missing
Typically a new screen is required (see item 1 for prices).
Warning, if you have an ultra thin laptop/notebook, parts are considerably more and can be difficult to source. Please be wary if you are quoted reasonable costs as these units really need to be seen before a confirmed price can be given.