Thought I'd post this for reference as it has come up previously:
Great Yarmouth (Gt Yarmouth, Norfolk) is somewhat lacking in public slips. The nearest to the North is all the way round the coast at Blakeney and Morston (about 30nm), the nearest to the South is Lowestoft (aprox 10nm).
There is one viable option; next door to the Yarmouth and Gorleston RNLI station (NR31 6PU). It's a decent concrete slip, and there's a pay and display carpark a moments walk from it. It is however pretty steep and very narrow; if launching anything sizeable you'll need a decent 4x4, and I'd recommend two people as there is nowhere to tie your boat up once launched so really someone needs to drive the boat off the trailer and hover by the slip while the other person parks the car etc.
I did a few recent visits at various states of the tide to establish a useable window. The slip drops off in line with the quayside so you're limited to how deep you can go (don't fall off the end as it's a long way down after!)
A realistic window (for a smaller RIB) seems to be around 3 1/2 hours either side of HW. Photos one and two were taken 3 1/2 before with a tidal height of 1.6m. The one showing the drop off was taken 4 hours after with a tidal height of 1.3m
Hope that might be of use to someone one day