I’m not sure which event you are looking to attend as there are two for miniature engines:-
Hollycombe Model Weekend - is 3rd /4th Sept; to enter that email
info@hollycombe.co.uk
Steam in Miniature is held in May; this is an Annual Rally for West Surrey Model Traction Engine Club (WSMTEC) members plus an amount of visitors.
The rally is a very relaxed weekend with the emphasis being on having a good time; there are some guidelines to running engines around the museum but a lot of common sense is applied.
The club membership has a variety of engines from 2” scale up to 6” scale; most years there are approximately 35 engines on show, the museum usually opens both days.
I’m the organiser for the WSMTEC rally, the 2017 date has not been set yet but will be in May; PM me your details and I’ll see what we can do for next year’s event, invites go out in January.