I can only recount my own experience of this.
At the end of May 09 I flew out to Canada from the UK (visa exempt) I was staying with my then fiancée for 50 days and during this time we got married and had our honeymoon in Canada. I returned on my own, to the UK, in July and we started the outland process. I, like you, was worried so I got in touch with Canadian Border Services and asked them what sort of problems I might have, also explaining my exact circumstances, they forwarded my e-mail to the Consulate in London. This is the reply I got from them:
A British citizen does not require a temporary resident visa (TRV) to enter Canada as a visitor. If the person is not otherwise inadmissible to Canada, this mission is unable to provide any documentation that would assist them at the Canadian port of entry.
When arriving in Canada, the officer at the port of entry will ask a few questions to be satisfied that the traveller will respect the terms and conditions of their stay. In addition to having a valid passport in their possession, the officer may wish to see proof of employment/studies in the traveller’s country of residence, evidence that they have sufficient funds to support themselves for the duration of their stay, a clear purpose for the visit, a return ticket and sufficient ties to their country of permanent residence. If your intention is to get married, the officer will ensure that you will leave Canada at the end of your intended stay and begin the sponsorship process from abroad.
The above considerations are merely a few examples of the issues that will be examined at the port of entry. The overall circumstances on the day that the person presents themselves at the port of entry will be taken into account.
As a result of this I put together a little pack of evidence to prove that I intended to return to the UK after my trip. This was quite difficult as I am self employed and so I dig out any evidence that I had an ongoing business that was going to carry on after my trip.
When I arrived at the 'border' at Halifax Airport the Border Services lady asked me the purpose of my visit and I explained 'exactly' what I intended on doing during the 50 day trip and then when I was returning. At the end of my explanation, she said, Congratulations, and stamped my passport. That was it, she never asked for any proof of return, but it was so reassuring that I had the stuff on me if it got difficult.
Be careful not to tell an outright lie, so my advice would be, don't give out more information that you feel you have to, but make sure you have evidence to back up your intention to return if they start to ask more probing questions.
Hope this helps.
