A single supply?

We publish a specialist newsletter and home-study course. Newsletter subscribers pay an annual fee for a monthly newsletter and unlimited 'password protected' access to online archive material. Very few subscribers actually use this service. Subscribers and students are also guaranteed an answer if they send a question to our 'panel of experts'. There is no limit on the number of questions either can send to the experts as only a tiny minority of our customers use this free service.
The company is VAT registered. Newsletters and courses are zero rated but we re-claim any VAT expended. The cost of providing answers to the questions is negligible in proportion to turnover.
HMRC say that we should charge VAT for online access and the 'ask the experts' service. The company pays this itself — as the amount we agreed with HMRC was relatively modest — and we do not re-charge...