Onward ticket vs return ticket

[elmono]

I´m a British citizen with a British passport. I´ve always lived and worked in the UK, but have been travelling around South America for the last 11 months. I now wish to travel around Canada for a few weeks before returning to the UK. I can prove that I have sufficient funds for my stay in Canada (via a bank statement printed from the internet) and have two credit cards with me. I also have the address of a Canadian citizen (friend) who can vouch for me.

Now, the problem...

The Canadian immigration website says that to visit Canada I need a return ticket, but I only have a one-way ticket (from South America).

Now, my question...

Is a seperate, onward ticket to the UK as good as a return ticket? I´m happy to buy an onward ticket (Canada->UK) before I leave for Canada, but only if I am confident that the immigration officers will let me into Canada. Will the fact that I have been travelling cause problems?

I need to know very soon as I fly in a couple of days.

Many thanks in advance