I trained with Relate and worked as a counsellor for quite a long time, and stopped about 10 years ago when work and commuting took over. But even then, we learned to look at our own prejudices and how we would deal with them in the consulting room. "Nonjudgemental" was always the key word, and, I assume, still is.
Phoenix has the general idea; counsellors would work with the relationship; if there were "technical" problems then a Relate sex therapist might be suggested. They are the experts, not the regular counsellor. Though, as always, one couldn't stop a discussion about sex abruptly!