It is sadly true now, the police are not allowed to use any discretion now with this issue, so even if they believe you they still have to take your car, and you pay for it.
Not all insurers are as quick as they should be, they have in theory 3 days to log the cover onto the system, but some take months, for which they are now being fined.
Your problem is the broker cannot update the MID, this can ONLY be done by the insurance company, so if they are shut at the weekend ?
Not worth the risk imo, speak to INSURER monday, NOT broker.
tabetha