This is an updated guideline from the FSRH on how to investigate and manage women with abnormal bleeding on contraception. I don't think there is much new here, but there are a couple of excellent flow charts which summarise the management.
One nice point is that it gives advice that women don't all need to be investigated if the bleeding is short lived and in the first 3m of use of the method.
There is also a really nice table that outlines different bleeding patterns that can occur with different contraceptive methods. I haven't attached that, but it is a really useful table to reference.
I am attaching copies of the flow charts from the FSRH guideline below.