both typres you refer to , ie decreasing cover and level term cover are available with most if not all life assurance companys. these policies are not necessarily being provided by the mortgage lender, most lenders are tied agents to a particular life assurace company who underwirte the policy. eg PTSB tied to Irish Life, AIB tied to Ark life, BOI tied to lifetime , ICS are not tied and have a number of agencies, your not under obligation to take a life assurance policy with your mortgage lender, your only obligation is to have a decreasing policy for a minimum of the mortgage balance and the mortgage term. best option is to talk to a broker who has a few life assurance agencys - they will go through the different type of policies available.
HTH