I have a slightly binding offside rear brake which can't be helping

I think it may be one of the pads stuck tight in the carrier. I seem to remember one was really difficult to get in when I did the rear discs and pads, although this was about 18 months ago.
Before I strip it down, how " snug" should the pads fit in the carrier?
I think there is another issue with the poor mpg but one step at a time

Thanks
Andy
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