A joint policy would be cheaper but generally not by much.

If you have a joint policy and one of you claims the policy ends, whereas if you have a policy each and one of you claims the other is still covered.

 If you split up in the future you walk away with your own cover, whereas alot of people would not want a policy where an ex partner benefits from your demise. There are ways round it but separate is easier.

As a very rough example say a joint policy costs £25 and two separate ones cost £15 each you are getting double the cover for that extra £5. Up to you as to whether its worth it.  

There are valid reasons why you would do this (e.g if repayment mortgage, allows for some future borrowing without further need for insurance. Can use current plans more easily if you split up in future, double the cover, not much cost differential if young  etc) but this would depend on the conversation you had with your adviser. It sounds more like you've been told rather than advised, which is probably to do with commissions/bonuses.

Go back to the adviser and ask for clarification. If they are not independent e.g.an employee of a bank or building society, then you would be better seeing an independent adviser locally to get the best and most suitable deal.

My girlfriend and I recently bought a house together in joint names and our financial adviser has taken out level term with critical illness policies for each of us separately. Is this the most efficient means of doing this as I would have though a joint policy would be cheaper. Does the fact that we both own other houses in our own name and as such have existing life assurance policies on these affect this?

Thanks