Who holds the debit card for the bank account in the trusts name? In other words, who has access to the assets of the trust?

The trustees have the legal access, but in practice, the manager can have the practical access, if that is the desire of the manager and the trustees. This means that the trustees would have basically signed a minute authorizing the manager to have such access, and then the manager would handle the day to day practical business of the trust according to the agreement s/he will have signed with the trustees. The terms and conditions of that agreement are entirely up to the preferences and the discretion of the manager and the trustees.