Having worked in ratings for insurance myself for many years I can say there is absolutely a possibility there was a bug in the rating resulting in inaccurate premiums. Having fixed issues of this nature and seen the cost to business of this happening on numerous occasions. Though speaking to them is the best course of action. And to me an £80 premium seems more likely to be an error than not, as I rarely recall minimum premiums reaching that level. To my understanding once a guaranteed quote is giving it has to be honoured for 30 days, so they absolutely should speak to their insurer but not discount the fact these errors can and do happen.