I've found cheaper rates for a UK hotel.
One thing that bothers me though is that
A guest must book the lowest available hotel room rate through the Best Available rate search
Which means the Non-refundable rate, (unless I'm mistaken) therefore if you lose the Best Price Guarantee claim you can't cancel the Holiday Inn.
The cheaper night I've found is non refundable on the HI site and refundable (10% fee) on the 3rd party web-site. So not exactly the same