Not fished the Uck for years (grew up there), don't recall myself or mates catching pike in the Mill pond or upstream of the road bridge. All the ones I've caught were downstream, through the industrial estate and just past the bypass.
As far as I'm aware, the owners of the mill don't let people fish there now and not sure if you can still cross the over spill section (Waitrose car park side of railway line), onto what we always referred to as "the triangle", then you could access the mill pond under the railway bridge.
If you can still walk the river bank through the industrial estate, park behind Carpet Right (I think it is now), you may be able to fish from the road bridge all the way down. If going beyond the first right hand bend, you might as well park on the bridge that crosses the river in the middle of the estate. you can access the length of the river through the industrial estate from here.
If you want to try just beyond the bypass, there are a couple of gateways either side a few yards to the south of the bridge, that you can fit a car/van into without any problems. There is a small weir about 100 yards (from memory) downstream of the bypass bridge.
We were always told downstream of the high street bridge was Isfield Angling Club waters, but I don't know of anyone who ever saw a bailiff from the club.