Advice please

[RoyW]

Gulls are confusing, and a major headache to work out - that's what makes them fun!

If only one of the first gulls you saw had yellow legs, then it may have been a yellow-legged Herring Gull (not something that you would expect to see regularly in the UK), or it may have been a Yellow-legged Gull or a Lesser Black-backed Gull.
It sounds like the darker ones you saw later are likely to have been Lesser Black-backed, but that doesn't help much with the earlier one.

[Deb London]

Thanks Roy.
Yes, I will try and view this as fun.

[Shrike]

Theres also the smaller common gull which has yellow legs and a slightly darker grey back than herring gull. These aren't very common but much commoner than yellow legged gull.

[Deb London]

Yes indeed. Luckily there were a couple of these for comparison.