You would not be entitled to a PAYE tax credit, you may be entitled to a personal tax credit. If you enter the details on ROS you should be able to see.
I don't think this is a good topic for a poll. Its a matter of fact not opinion.
You are liable to tax on your rental profits. Even though the rent is less than the mortgage you may still have a profit.
The capital part of the mortgage is not a tax deductible expense. Only 75% of the interest payment is tax deductible. In practice you should receive an annual statement from the bank showing how much interest you paid. 75% of this is a tax deduction.