Quicky – buying on credit card

What is the threshold at which you are covered by the cc company rather than direct to the supplier in case of problems?

I think it’s £100 but not sure.

Then as follow up – if you’re buying, let’s say a bike, with the intention of paying cash but are asked for a deposit to secure while you make arrangements to get the cash and go to collect the goods – if you pay >£100 on a cc as deposit, are you then covered for all the goods (suspect not, but not sure)

According to Martin Lewis, if you buy an item that is more than £100, and any part of that is on a Credit crad, you are covered.

thanks