One of the reasons that the ONS is not including a question in the census about sexuality is because they don't believe that they will get an honest enough answer. This is the first time that this question has been asked in any national survey and the expectation (and previous experience of questions such as these) is that over time the numbers will increase.
There are some statistical anomalies in the figures themselves, the vast majority of gay people are in the under 45 category whereas only 50% of straight people are, suggests that the older people are the more likely they are to be reserved about their sexuality.
Anyway, at the end of the day does it really matter? 1 in a hundred or 50% of the population, gay people still exist and are still a part of society and contribute to the production of television programs whether it is by paying the licence fee or buying the products advertised.