No MOT is a minor traffic matter, especially if its only just lapsed a day or two before. If it does go to a hypothetical magistrate he/she'd be a co*k to throw a big penalty your way.
However, fail to produce is serious sh1t & can lead to disqualification, especially if taken into consideration with other offences (no MOT for example?).
Don't blag it, its not worth it. You won't pass under the radar as if its on a ticket its likely the local ticket office has it on the system waiting for the fine & the HORT2 (the form that's filled in with your document details when you turn up) to come back, otherwise its a NIP in the post m8.
If it was just a producer, possibly could slip through the radar as its the PC's responsibility to keep a check on when the HORT2 comes back, but in all honsety most are pretty hot on this.
Good hypothetical luck!