Affiliate Marketing Secrets

My car is due for it’s Insurance renewal, however rather than going with my current provider I have decided to visit a few price comparison websites first, to see if I can get a cheaper quote. First up I went on confused.com and started filling out all the usual details but then came across the section where they want me to provide a value for my car which has really stumped me.
I know how much I bought the car for and I know that obviously it’s value will have greatly depreciated since, but not being affiliated with the motor trade, how can I possibly ascertain it’s value?
Are there any reliable and trust-worthy websites I can use to make an evaluation?
It would have been good if confused.com provided a means of calculating my car’s value.
I don’t really want make an estimate (although) tempted in case I am well off the mark and end up invalidating my insurance.
What a quandary to be in just to meet the obligation of a law-abiding motorist.
If anyone can help me with this matter,
I look forward to hearing from you