The only Amiga events I'm aware of are organised by the Amiga North Thames group:
http://www.amiganorththames.co.uk/However, we do have other retro computing and gaming events in the UK, for example Retro Revival:
https://www.facebook.com/FusionRevivalPlus, the demoscene is still active and we have a fantastic event once (recently twice!) a year down on the South Coast:
http://sundowndemoparty.net/The North Thames events are probably the closest to what you're looking for. The Retro Revival event is great (multiplatform) family-friendly fun whilst Sundown is mostly booze fuelled with huge projector and sound system, late night partying and BBQs on the beach at 2AM
