If you are lucky you might not have to necessarily change the entire window regulator system. What this means is that you only need to change the clamps. In which case, you obviously upgrade to the metal type ones! You can pick up repair kits of course which will include the stronger metal clamps and cables: around £40 inc VAT
The worst case scenario, if more damage has occurred, is to change the entire inner door skin. Budget around £85 for this. But, for the love of God, don't get cheap replacement parts from the likes of 'bay, etc.! Remember: buy cheap, pay twice!
The question isn't 'if' the window regulator clamps will go, it's a question of 'when'...