American in UK

Hi my name is Kirk and my son Gavin is Autistic.  Diagnosed with Pervasive Developmental Disorder no otherwise specified.  Translation-"got me we have no clue". My wife and I love to travel and we would like to come back to the UK for a visit.  The issue is we would be bringing our 8 year old autistic son this time. Last time we were there we were newly maried and childless. This may be a silly pointless post but here it goes.  What tips does anybody have to somebody traveling with a special needs kid in the UK.  Do we need a car seat with us like in a taxi.  Just silly questions like that.  Any tips you have would be appreciated.  If you wan't to know anything about autism in the USA let me know and i'll be glad to share what i know.

Thanks

Kirk