The Yellow-legged Gull was in the roost at about 3pm yesterday. There have been 2 adults in the roost recently, in fact the second bird could have come in yesterday as I didn't stay until dusk for the full roost. Basically, if you go on anytime after 2.30 and stay until dusk you should be in with more than a good chance of getting the Yellow-Leg. The large Gulls tend to arrive on no 1 Reservoir first to bathe and preen.
Can you report the Golden Plovers to the BTO website as described in the "sticky" message at the top of the forum listings? Apologies if you've already done this.