Hi Mark,
I think that your little birds are most likely goldcrest - I've got photos in my gallery (and attached) of goldcrest that are so "plump" that they're football-shaped!
The thinner song is better for gold too - fire has a slightly lower pitched call (though there's not much in it until you've heard both).
Oh - and firecrest is rare enough that to have seen "a few" would almost be a national event..!
I can't think of a single good reason why you shouldn't post in exactly the way you just have: you were on your patch, you saw some birds and asked a few questions - seems to me that's exactly why we've got this thread, and I for one will post similar questions here whenever I'm not sure about something.
Don't think you've got anything to worry about there, Mark.