Norrie,can't offer you any first hand experience of click4warranty but after a lifetime spent in the insurance business I would say be very careful.
As with all insurance products you need to read the small print very carefully.My own feeling is that a lot of warranties are similar to the loan
protection /redundancy policies that banks try to sell to people taking out loans ( sic) ie they are not worth the paper they are written on.
You need to understand the exclusions/what is not covered and just as important what is covered if an excluded part breaks and is the cause of damage to insured parts.In this scenario you may find NOTHING is covered.
Lastly,don't take advice from the people selling the product ,read the small print yourself and make sure you understand it.
Good luck

P