It is just over the limit for a fixed penalty fine.
However, the reality is that they may just give you the FPN. They can do that when it suits them.
There is a risk of a summons. That would lead to 4-6 points and a fine of between 75-125% of your weekly income and costs of £85.
However, the reality is that I would expect them to just levy the FPN. You are only 3 mph over the cut off point.
Can I clarify anything for you?