[gerdesj]

I would say yes. Some of the answers here are referring to population stats and you are worrying about your particular circumstances, which is different.

If someone you come across (family, stranger, whatever) keels over you need to, without proper medical knowledge, diagnose the issue and then administer appropriate treatment. Oh and could you do it within a couple of minutes please.

CPR should be a last resort - it can be rather barbaric. A defib has a way better chance of success and won't break your ribs.

A defib costs around £1000 or so. Hopefully that money is wasted.