In case anyone is in the same situation I was, Billy's in North Shields is open in the mornings from 9 am. You can click and collect, or you can turn up when 1 person at a time is allowed into the shop. Cash only though.
I got all the heavy sinkers I needed, as well as items such as jig heads, savage eels and a bulky landing net. Billy thinks he will be able to open fully on 15 June.