You think price means anything? You fool. What brands did they carry? Which brand was the one you tried? Until you can answer that, you have been proven wrong.
Let's just go back to the basics:
1) I have been drinking absinthe for over 6 years, I have tried dozens of brands of varying qualities from all over Europe
2) You drank it "a few times" in UK, and have "no idea" what brand you tried
3) UK is famous for serving terrible quality "absinthe" - the same cheap fake crap that gets sold in BC
4) You are saying that you didn't experience a secondary effect
5) Somehow, this means you are an expert on absinthe, and telling everyone who knows better that they are wrong.
And finally, you're the one who brought up Thujone, not me. Whether that is the active ingredient that gives the secondary effect is unknown (it may just be the mixture of other herbal ingredients that do so). In any case, a good, proper distilled absinthe will give a secondary effect. Drinking cheap British coldmixed crap will give "intense drunkness" and nothing more.
And anyway, the "secondary effect" shouldn't be your main goal when choosing an absinthe to buy anyway. Like any other good spirit, you need to consider flavour, colour, and other subtle things that make a drink special. If you are looking to get 'high' or even experience some lucidity, you are better off huffing a can of paint or something.
EDIT: looking at
the site for the store you went to, they do sell
one good absinthe (Clandestine) but the rest is complete utter crap (yes, every single one of those 11 bottles is garbage). You can check the reviews
here.
So I assume you are suddenly going to remember what brand you tried, and it was certainly Clandestine, right? If not, there is an 83% chance the stuff you bought was cheap coldmixed crap.
Hopefully you don't get all upset again, and can begin to accept facts.