Statutory rights under the Sale of Goods Act gives only 12 months cover and as it is 18 months old it is out of warranty
Did you take out extra insurance?
Could try Marct`s way and contact the company but don`t hold your breath, that is why insurance is there to cover for any mishaps, maybe you thought why should I pay a premium for something I may not use, well welcome to the real world.
I NEVER pay for extra insurance as most things go wrong in the first year, but after that if it goes wrong I take it on the chin and don`t expect to get the same cover as an insured person.
Ask a tv engineer for a free quote for repair sometimes this is cheaper