Decathlon, or "D4" in France, this is a mixed opinion for me.
They hugely contributed to sport outreach in France, Belgium, Spain...
Hugely successful... and so agressive to small businesses.
My lovely local tackle store in the village I was grown closed down because of them, a year after they settle a store.
Real tragedy, as the owner was a sweetheart. He was my main fishing teacher (as yes... we have official fishing school there!!).
Then, I did myself purchased so many articles from them.
But I think the market in UK is very different. Sport stuff are cheap compared to the rest of Europe, people want quality and brands. We do find good quality in small tackle shops at good price, in other outlets such as Go Outdoors etc. Even Sports Directs sometimes sells a Buster Jerk for £6.
Still the fact Decathlon is still here demonstrates quality of their products. Also I love going with my daugther trying all sort of scooters, bikes, fishing equipment, running shoes... I do not know a single store doing this in the UK. Trying before buying, that's their point.
In Valenciennes and Tenerife, the stores are absolutently immense. Anything (and more) which is on the website will be ready on display.