Apologies. I was wrong about UK thanksgiving. At my church, they read out the proclamation by Queen Elizabeth II declaring the second Monday in October to be Canadian thanksgiving and I guess I've always incorrectly assumed it was the same in the UK. So many customs, laws, systems (and even the monarch) are shared that it is a surprise to find exceptions to the rule.
Apparently in the UK there are harvest festivals and some special church services in November, but it isn't given the same treatment as in the US and Canada.
It's really the Morris dancers you need to be aware, and wary, of.