Going to Canada from England as an overstayer in England.
If you already have a valid visa for the above country then you can if not then you cannot.
Is it at all possible without returning to the home country?
Yes if the above answer applies to you i.e. you already have a valid CND visa in your passport despite the fact that your stay in the UK has expired. If you don't have a visa, I'm afraid you cannot.
travelling as a spouse of someone who is eligible to stay under the points system.
I'm assuming you meant your spouse qualifies under one of the permanent residency categories in Canada. Correct me if this is not the case.
AFAIK, you need a valid visa for your spouse to apply for migration even if you are a spouse of the principal applicant. You need to submit a copy of your passport and residence permit at the time of the application and this can cause problems later on if they want to verify.
(NB: Please note that, due to the new process (simplified application process), you do not need to submit any documents at the time of filing your application apart from the application fee. If you can sort out your residency status in the UK by the time your application comes up for review say 24-30 months time then, go ahead and let your husband apply. If you cannot, I'm afraid don't)
Your spouse is better off applying from the country of his/her citizenship so that both of you would be safe assuming he's not a UK Citizen. Alternatively, sort out your illegal status in the UK first before your spouse applies.
Good luck.
