Personally, I've never agreed with the mainly religious belief that there is virtue in suffering. It seems more humane to let people decide for themselves when life has become too burdensome to continue.
It sounds as though they're reluctant to be labeled a 'death tourism' destination. The UK anti-euthanasia group Care Not Killing that's in favor of the referendum is an umbrella group of about 50 organizations including human rights and disability rights groups, health care, palliative care groups and faith based organizations.
Key groups signed up to Care Not Killing include: The Association for Palliative Medicine, the United Kingdom Disabled People's Council, RADAR, the Christian Medical Fellowship, the Catholic Bishops Conference of England and Wales, the Church of England and the Medical Ethics Alliance.