I'd like to consider myself somewhat acquainted with LAN parties.
I used to regularly attend the Multiplay i-series LANs, then staffed them as both a yellow shirt and a red shirt, I also attended and still do attend the smaller Multiplay Stratlan events.
There's the relatively recent and excellently run
epic.LAN events way up in Uttoxeter near Stoke. I also attend a number of smaller (20-50 person) sized LANs throughout the year (including a private one where about 20+ of us go to a rented village hall near reading / newbury in the summer and have BBQs, drink and maybe a little gaming if we feel like it... A lan PARTY if you will, rather than a LAN Party...

)
However LAN parties have never taken off in the UK the way they have over in Europe or the US. The UK's only big lan, the i-series is primarily aimed at the professional gaming market, which for me isn't much fun and the atmosphere isn't so good. In the rest of the world, pro gaming takes a back seat to fun and atmosphere.
For the last couple of years a group of us (a mixture of Multiplay and epic.LAN staff and regulars) have gone over to Sweden for Dreamhack Winter. 10,000 + gamers, a massive PA with a lighting rig most nightclubs would be very jealous of and more hardstyle music than you can shake a stick at (not to mention other appearances by live bands such as
Scar Symmetry). The atmosphere is incredible and there's just nothing quite like it.
And of course, we made sure that people knew where we were from, if the loud shouting didn't give it away already...