Since i started hacking at wood I go every year.
I've been twice so far and will go again this year, but then i'm not that far away. I'll probably spend all day there drooling over tools.
Prices are a little better than in the shop depending on what they've negotiated with the manufacturer, but not a huge difference so you won't make huge savings.
Trend have had a huge stand, I assume displaying everything you can buy from them including router tables.
Record Power have their own room including demos...whenever i went in there there was a guy on the lathe with a seated audience.
Festool have a big stand with demonstrations - last year i noticed there was a Festool lorry with demos too
Scheppach have a stand inc. demonstrating scroll sawing
Makita, Dewalt and Bosch have big stands although i don't recall there being demos.
Hand tool manufacturers are also represented, but it's primarily a power tool show - Veritas had a stand last year and i might get a router plane but it depends how much they are.
I must admit, i thought DM Tools only did the one annual show in Kempton Park as that's the one they advertise on their website. I'm not sure the other shows you've mentioned are run by DM Tools as the descriptions don't seem to fit, the one in Kempton Park sounds better than those described above.
The only downside is i have to figure out how to get the stuff i've bought into the garage without being spotted.