A pair of grey wagtails in the stream bed. I saw them yesterday as well.
Not seen by me, and not today, but last week there were twitchers in the park hoping to see a firecrest. One chap with a hugely expensive DSLR and long lens showed me a photo he had taken of it. I might be able to tell a firecrest from a goldcrest if they were kind enough to sit side by side on a branch in front of me for a few seconds, but otherwise I doubt it. I just assume that everything I see of that ilk is a goldcrest.