This is very typical of payment protection insurances and they are probably using the "pre existing illness" get out - although I would appreciate your argument that this is a different injury.(posted 7018 days ago)You may want to consider going down to your local CAB office who have a lot of experience with this particular issue and will write to your mortgage lender and the insurance company on your behalf. Make sure you have ALL documentation with you before you go.
Double check with DWP in case you qualify for help with the payment of the interest on your mortgage.
Good luck and keep us posted.
Moira