Spouses/common law partners are exempt from meeting the medical/criminal requirements for Permanent Residence, so no, you won't be denied (for this reason, at least). I am almost certain it will hold up your application though.
This statement is absolutely, positively, unquestionably WRONG . . . spouses/common-law partners are exempt from meeting most medical requirements - but they are absolutely NOT exempt from meeting criminal requirements! Canada has zero tolerance for criminality of any kind - no matter how insignificant the offence might seem. If you got arrested, you're "bad" . . . period (not my judgment AT ALL, believe me.) IF you have a criminal record, you are going to have to meet the rehabilitation requirements before you are eligible to immigrate. Frankly, trying to immigrate when you have
anything on your criminal clearance is a cr @ p shoot . . . they're going to delay processing for months while they determine the equivalency of your charge/conviction to Canadian law . . . in other words, assume the offence had happened in Canada, how would you have been sentenced in Canada? Then depending on the "Canadian equivalent" sentence, and how long ago you satisfied whatever restitution you were ordered to make at home, they will determine whether you are eligible to be "deemed rehabilitated". It's very complicated and very subjective.
My advice: get all of the information pertaining to ALL of your offences put together, get your criminal clearances so you know what shows up on your record, and have your partner meet with a
qualified Canadian immigration attorney BEFORE you submit any PR application and BEFORE you give up your life in the UK and come to Canada. It's imperative that you know where you stand because, if you are eligible to be deemed rehabilitated, you're better off to submit the paperwork to get that certification first - and then include it with your PR ap. If you leave your "deemed rehabilitated" to some VO who's assessing your permanent resident application and they're not comfortable with making a favourable decision on your behalf you'll be looking at months and months of delays, and then a refused application that you'll have to wait even longer to satisfy in an appeal (IF you win the appeal). Take my word for it - criminality, even if it isn't your own (I got refused because my adult son, who isn't even immigrating to Canada, has a criminal record - read my profile signature) is a
serious issue and you do not want to go into this process with any misconceptions about where you stand in that regard. Don't put yourself at a disadvantage - be informed and put yourself in the best possible position before you put yourself at their mercy . . . otherwise you'll be banging your head against a brick wall for years.