^^ as above, all home remedy will only last a few months, max 10-12 months and you'll have to repeat again. Best is to get them done by a bodyshop. They'll lightly sand down and apply a layer of clear coat usually they are UV protected as well. This should cost around £40 to £60 for both and will last 2-3 year minimum (depends on the clear coat they use). I uses the Maguiar's Headlight restoration kit and finish with few coats of Turtle Wax ICE wax paste for UV protection. Last about 7-8 months before i need to repeat. £20 for the kit, £15 for the wax, FOC for labour (around 1 hour). Still works out cheaper compared to bodyshop
Edit: The kit I used was the older kit (sand down and polish), newer kit seems better --> http://www.halfords.com/motoring/car-cleaning/clay-bars-detailing-products/meguiars-2-step-headlight-kit