I believe Lionel also make a ready to run Thomas in O gauge, and some of the other locos too, including the evil diesel shunter - a fair representation of a British Rail class 08 shunter.
I remember seeing the Rev. Awdry's OO layout at a model railway exhibition in Bristol, England, many years. Some of his models, including those of the narrow gauge Skarloy Railway (based on the real life 2' 3" gauge Tal-y-llyn Railway in Wales) are now on show at the Tal-y-llyn Railway's museum at Tywyn in Wales. Well worth a visit, even if you don't have time for a ride on the TR!
From a modelling point of view 16.5mm track is not really accurate to represent 4' 8.5" gauge in 4mm: 1' scale but most UK model railroaders have always lived with that. For modelling the Tal-y-llyn Railway however in 4mm scale, N guage track is spot on so this scale/gauge combination has been popular here for many years.