I found this a really challenging subject. National holidays / celebrations immediately sprung to mind, but I've been a bit blase about Halloween since I turned ten, we don't really do Valentines' Day, Shrove Tuesday is good but nothing to shout about and as for Christmas... Last year we didn't even put our tree up. I wanted to do it in early December, but didn't and by the next time we thought about it, it didn't seem worth it. We made do with a little eight inch high tree on a coffee table.
I guess then there are British traditions. One of my friends lives in a town where there is an annual folk festival. I love a good wander round, taking a few photos of the Morris dancers (a prime example below!), but I wouldn't say it was my favourite tradition, any more than fish and chips at the seaside. I have fond memories of country dancing and maypole dancing at school, although you can bet I didn't have fond feelings about it at the time. I can't imagine many schools do such things any more. Whilst I'd love to live in a traditional village which had a summer fete and such things were practised, again I don't think they're my favourites.
That brings me to thinking about the traditions we create ourselves, daft things like we always have a second Christmas dinner for New Year, we have our own way of serving up fajitas and have curry the night before we get the ligatures changed on our braces. I'm sure there must be more. I guess that's what I love; these little traditions that are specific to us.