Eurostar waiting area

Does anyone here know of or have used a special autism-friendly waiting area in the Eurostar London St Pancras lounge? During one of our trips there I noticed a young boy with ear defenders sitting behind glass doors in a separate area, the doors were one way only so I couldn't get in. This area was visible from the far right corner of the lounge past the information desk and the regular assisted travellers area.

When I was about to travel again by Eurostar a few months ago, I called the special assistance number. The person I spoke to said to be based in Ashford and wasn't familiar with the London terminal layout but made enquiries and came back to me confirming there was a quiet area accessible for people with autism, just off the business lounge. However, on the day of travel the people at the special assistance desk had no idea what I was talking about, made a phone call and then insisted there was no such area and that the only way to enter the business lounge was with a valid ticket. :( 

They do have a person take you through the staff entry bypassing the queues for passport control, luggage checks etc and you are taken to the regular assisted travellers area. The problem is that regular passengers also sit down there, ignoring the sign at the entrance and staff don't send them away unless they take people to the area and find there is no space to sit them down. Parents with small children think the area is also meant for them (not entirely sure if it isn't) and so it gets extra noisy. The entire lounge is very noisy and overcrowded anyway, and so my son finds it unbearably noisy and feels the need to stim to cope but too self-conscious to do when sitting in a crowd of people. So a very stressful experience.

The lounge in Ashford International doesn't have a special assistance area but is much smaller and quieter, then again the train we catch from there only leaves once a day, very early (6.54 or 7.28).

Anyway, if anyone has had better luck travelling with Eurostar from London I'd love to hear from you.